A Survey of Searching for Secret Doors
I rolled an investigate check
Reddit Thread
I think of all the systems that I’ve read attempt to describe task resolution, Simulacrum does it best:
The default assumption is that players must overcome a challenge by describing what their characters do to meet it. This need not be an exhaustive or even heavily detailed narration. In fact, it’s usually better if it’s not. All you need is a broad statement of what the character hopes to accomplish, and any interesting ideas that might make it easier than normal—this is where player skill comes in.
The GM might decide that the right description is enough by itself to resolve the situation. If not, a specific character ability might be relevant instead.
Failing any of that, the Task system is used. The idea is that you roll to resolve situations with interesting stakes that would
be too tedious / difficult to describe, or
involve a strong element of chance
This is exceedingly practical. Describe what you’re doing and how until the folks involved feel like they’re out of their depth. There are a bunch of different activities that I don’t feel qualified to just talk about.
“Yeah so you have two low feet holds; pegs basically. You feet are about a foot apart, your right one about 4 inches higher than the left. You left hand is in a two-finger pocket and your right hand is in a gnarly crimped side cling. You’ve got a higher left foot that would put you into a drop knee and then could gaston over to…”
The big ones that come up are: climbing, jumping, knowing setting-specific information, swimming, haggling, stealing, stealthing, but most of all…
Searching
I think searching is very important to get right because it embodies what I see as the biggest difference between OSR play and 5e play. When I’m attempting to explain old school D&D to 5e players, the main contrast I draw is “When you want to search a room in 5e, you roll a perception check. When you want to search a room in the old versions, you explain what you’re doing. I tell you about the bed and the tapestry, you tell me you’re looking between the mattresses or behind the tapestry. Touching that stuff is potentially risky, so deciding what to touch and how to touch it is a big part of playing well”.
That’s fine as long as there’s something (a bed, a tapestry, etc) to latch onto. What happens when the you want to search a nondescript section of wall or floor?
A solution I often see is some combination of Knave 2e’s guidance on searching
Search Checks: Hidden things are either automatically discovered after enough time is spent searching (usually ten minutes for dungeon rooms or a full watch for wilderness hexes) or they cannot be found without taking in-game actions. Obvious features of an area should be described right away to PCs, and details should be described as players ask questions and investigate.
With Justin Alexander’s Matryoshka Search Technique
Instead of immediately discovering the item of interest, the character instead discovers an indicator pointing in the direction of the item of interest. The advantage is that it allows (and even requires) the player to receive information and then draw a conclusion. It’s a subtle distinction, but the result increases the player’s engagement and reduces the feeling that the GM is just handing them whatever information he feels like. I call it the Matryoshka search technique because it turns the interaction into a nested doll: One investigation “opens” new information, which can then be opened by another investigation in turn.
Applied, when the characters are moving at exploration speed (~100ft per 10 minutes), they automatically discover an indicator pointing in the direction of hidden stuff (traps, secret doors, etc). Then, they can investigate the indicator to learn more.
This is the sort of thing that sounds great in theory (at least it did to me), but doesn’t work very well with running real-life modules. Real-life modules are frequently not written to spec with the theory-of-the-week. Tons of secret doors and traps just don’t have indicators.
Here’s some examples
Blackapple Brugh, p35
Aside from the pit opening in the ceiling, the only other way out of the pit is a secret door in the south wall. It is only three feet wide, which would allow a small or medium-sized creature to squeeze through.
Stonehell, p21
Stone throne covered with adventurers‘ graffiti; broken tiled floor; dust & cobwebs. An open trapdoor leads to a pit (20‘ deep and studded with rusty spikes) set into the floor before the throne. A button on the throne‘s left armrest once triggered the pit trap, but the mechanism is now broken. The secret door in the north wall is of shoddy workmanship (+1 bonus to attempts to find it).
Secret of the Black Crag, p46
At the top of the pyramid stands a small temple housing the chieftaness’s chambers. Sish’s pet giant electric eel guards it day and night. A secret door in the floor conceals a staircase to a desecrated tomb.
The Forest of Gornate, p18
Halfway through is a secret door, leading to a side chamber with a forgotten treasury: rotting sacks contain 500 sp, 200 electrum, 550 gp, and 500 gp worth of glazed ceramics (requires cart or two horses).
Castle Xyntillan, p20
The secret door opens into a dank passage. Rotting bags contain 2500 sp and a pair of cut gemstones (2*500 gp).
Sinister Secret of Peacock Point, p15
Secret Door: A switch in a well-hidden finger-hold along the eastern wall clicks open a secret door to A24.
Treasures of the Necropolis, p10
A long-forgotten secret door leads to a dusty, zigzagging corridor in the cyclopean stone wall leading to P.
Khosura, p27
A secret door from the second floor of one of the shacks leads to UCII/B-11. This specific place is guarded by 8 robbers.
Morgansfort, p25
A secret door is located in the north wall, near the east pit.
and many, many more (side note, ripgrep-all is a fantastic tool for this sort of plumbing) exist.
So, we can either try to create indicators for all of this hidden stuff (either during prep or on-the-fly) or we can admit defeat and recognize that OD&D included (effectively) a perception check for a reason.
What follows is a listing of how how finding secret doors works in every OSRish game I have access to. Enjoy!
OD&D - 1974
Time spent searching for anything (secret passages, hidden treasure, etc.) […]. Typically, […] searching a ten foot section of wall for secret passages will require a full turn.
…
Secret passages will be located on the roll of a 1 or a 2 (on a six-sided die) by men, dwarves or hobbits. Elves will be able to locate them on a roll of 1-4. At the referee's option, Elves may be allowed the chance to sense any secret door they pass, a 1 or a 2 indicating that they become aware that something is there.
Very clear. You can search 10ft sections of walls (and not a big leap to assume 10x10ft sections of floor) in 10 minutes with success dependent on race. 2-in-6 for non-elves, 4-in-6 for elves. Elves also get a 2-in-6 to detect the doors (gm’s choice) just by passing by (PASSIVE PERCEPTION IN MY OSR?!).
OD&D is not clear on whether or not you can search again if you suspect a secret door to be in the area but didn’t find one.
AD&D 1e DMG - 1979
SECRET DOOR — checking for by simple tapping of floor or wall, by 10’ × 10’ area: 1 round (1 minute)
SECRET DOOR — thorough examination for means to open, by 10’ × 10’ area: 1 turn
[…]
Concealed Doors: These are doors which are hidden in some way — behind a curtain, covered with plaster, a trap door under a rug, etc. They differ from a secret door in that once their concealment is uncovered they are obviously doors.
Secret Doors: These are portals which are made to appear to be a normal part of the surface they are in. They can possibly be sensed or detected by characters who are actively concentrating on such activity, or their possible location may be discovered by tapping (though the hollow place could be another passage or room beyond which has no portal in the hollow-sounding surface). Discovery does not mean that access to the door mechanism has been discovered, however. Checking requires a very thorough examination of the possible secret door area. You may use either of two methods to allow discovery of the mechanism which operates the portal:
1. You may designate probability by a linear curve, typically with a d6. Thus, a secret door is discovered 1 in 6 by any non-elf, 2 in 6 by elven or half-elven characters, each character being allowed to roll each turn in checking a 10’ × 10’ area. This also allows you to have some secret doors more difficult to discover, the linear curve being a d8 or d10.
2. You may have the discovery of the existence of the secret door enable player characters to attempt to operate it by actual manipulation, i.e. the players concerned give instructions as to how they will have their characters attempt to make it function: “Turn the wall sconce.”, “Slide it left.”, “Press the small protrusion, and see if it pivots.”, “Pull the chain.”
This is, as far as I’m aware, the first time we’re explicit about narrative interaction sidestepping abstract resolution. You can either roll OR give explicit instructions that’ll just work. As we’ll see later, Dolmenwood does a fantastic job refining this idea. It reminds me of Taleturn’s Hidden Goblin (thanks for the link, Dave!) series where it claims that Apocalypse World is the first time the GM is explicitly and clearly told that they ought to be tracking off-screen characters and events.
It’s also the first time I’ve seen a clear distinction made between concealed and secret doors. Everywhere else either doesn’t bother to define the terms or uses them interchangeably.
Relative to OD&D, the success rates have been halved (2-in-6 to 1-in-6 for non-elves, 4-in-6 to 2-in-6 for elves). It may seem like elves lost their passive perception, but this rules section just omits it. The Elf section in the races chapter of the PHB has it:
Secret or concealed doors are difficult to hide from elves. Merely passing within 10’ of the latter makes an elven character 16 2/3% (1 in 6) likely to notice it. If actively searching for such doors, elven characters are 33 1/3% (2 in 6) likely to find a secret door and 50% likely (3 in 6) to discover a concealed portal.
Despite chances being lower, learning about the existence of secret doors is a lot faster. It only takes a round (1 minute) than a turn (10 minutes). So a character can check 1000sqft in a turn in AD&D compared to 100sqft in OD&D. This makes actually searching a room reasonable. The motivating example from this post is the Abandoned Priest’s Quarters from Winter’s Daughter:
There’s a loose flagstone in the top-right 5ft square and no indicator that it exists; the book calls for a search for traps or secret doors.
This is a 375sqft room with 750sqft of wall to check for secret doors. In OD&D (and as we’ll see, B/X), this would take 12 turns of labor (so it would take two searchers a full hour). In AD&D, this is much faster, taking the team of two just 1 turn. It makes it plausible to say “I search the floor for secrets” rather than having to specify the right 10x10ft area.
1e is not clear on whether or not you can search again if you suspect a secret door to be in the area but didn’t find one.
Basic/Expert (Moldvay) - 1981
TIME: Time in D&D adventures is given in turns of ten minutes each. A turn is not a measure of real time, but is a measure of how much a character can do within a given amount of time. It also takes a turn for a character to search a 10'x10' area
[…]
SECRET DOORS: A secret door is any door that is hidden or concealed. A secret door usually does not look like a door; it may be a sliding panel or hidden under a rug. Any character has a 1 in 6 chance of finding a secret door; any elf has a 2 in 6 chance. The DM should only check for finding a secret door if a player says that the character is searching for one and searching for one in the correct area. The search takes one turn. Each character has only one chance to find each secret door.
This is later contradicted in the example of play on B59:
Morgan: "OK, what does the room look like? We are checking the floor and ceiling, too."
DM: "The room is six-sided, 30' on a side and 20' high. The door you came in is the only one you see. There is nothing unusual about the floor or ceiling. Besides the bodies of the goblins, there is a wooden box along the northeast wall and a pile of old rags in the north corner."
Morgan: "Silverleaf is checking for secret doors, Fred is looking for traps, Black Dougal is examining the box, and Sister Rebecca is guarding the door. I'm prodding the rags with my sword—any movement?"
DM (after rolling for the appropriate chances): "Silverleaf notices that one of the stone blocks in the southwest wall is slightly discolored. Fred does not see any traps. The box is the size of a small trunk; it is latched, but not locked. Morgan: nothing moves in the pile of rags."
It seems like the rules are explicit that you can search 10x10ft per turn (and so would have to specify which 10x10ft area prior to searching. Yet in the example of play, neither Silverleaf or Fred specify where they’re looking and the room is much larger than one search area (3600sqft of wall, ~2300sqft of floor) and yet silverleaf finds the secret door right away.
Regardless, relative to OD&D the success rates have been halved (2-in-6 to 1-in-6 for non-elves, 4-in-6 to 2-in-6 for elves) to the same rates as AD&D (but take 10x as long as AD&D). Elves lost their passive perception.
B/X explicitly mentions that you can only attempt to find a secret door once.
Rules Cyclopedia - 1991
Any character may search for secret doors. The player must describe the exact area being searched. This takes about one turn for each 10' X 10' area searched. If a player says "My character will look for secret doors," roll 1d6. You should always roll, whether a secret door is there or not, to keep the players guessing. If there is a secret door and the result is a 1, the character has found the secret door. Elves find secret doors with a roll of 1 or 2.
Identical to BX other than not being explicit about repeat checks.
Seven Voyages of Zylarthen - 2014
Secret Doors and Passages: It will take one turn to search a 10’ x 10’ area of wall. Men, Dwarves and Halflings will have a 2 in 6 chance, and Elves will have a 4 in 6 chance of discovering such a door if it exists. In addition, Elves will often have a 2 in 6 chance of sensing the presence of such a door by mere proximity.
Alternatively, if gameplay time allows, if a player explicitly describes the actions of his character such that the referee decides that they comprise a rational and intelligent approach to finding a hidden door—“I will methodically knock each flagstone with the pommel of my dagger, listening for variations in sound”—then the referee may determine that there is a close to 100% chance of success, if such a door exists of course.
Totally faithful to OD&D, with an explicit callout for a narrative interaction alternative.
OSRIC - 2006
Searching for hidden treasure, traps, secret doors, and whatnot: A common activity. Looking for secret doors is a time-consuming process, taking a full turn for each 10 × 10 ft area searched. Even so the chance of success is small: 1 in 6 for most characters, with elves and half-elves having an innate advantage (translating to a 2 in 6 chance).
This is one of the areas where OSRIC is not faithful to 1e. These are effectively the rules from BX, not 1e. We also drop the definitional distinction between concealed doors and secret doors but maintain the mechanical differences (elves have a 3-in-6 to find concealed doors vs 2-in-6 to find secret doors). OSRIC is wild.
Basic Fantasy - 2006
I have the 4th edition, and am too lazy to check to see if there have been significant rewrites between the various 100+ versions, so if someone finds one, please let me know and I’ll edit!
Under normal conditions, searching for secret doors takes one turn per character per 10' of wall searched. A secret door is found on a roll of 1 on 1d6; characters with 15 or higher Intelligence succeed on a roll of 1-2. Also, as noted previously, Elves add 1 to the range automatically, such that an Elf discovers secret doors on a 1-2 on 1d6, or 1-3 if the Elf has an Intelligence of 15 or higher. The GM may create secret doors that are more difficult (or easier) to detect at their option.
Multiple characters searching for secret doors ensures that any such will eventually be found; however, if the first and second searchers fail, the next searcher must take two turns to search, and all subsequent searches of the area require an hour.
This is effectively BX but with an intelligence bonus and confusing language around how how multiple searches work.
It says “multiple characters searching for secret doors ensures that any such will eventually be found”, but I’m not sure how that’s the case. If 4 people search the the same area, it’ll take 10 minutes, then 10 minutes, then 20 minutes, then 60 minutes (1h40m total). If all of them are normal-int non-elves, there’s still a
48% chance that none of them find it. Even 30 characters searching (for 27h40m) still gives a .4% chance to not find the door.
Basic Fantasy implies that a character can’t search for the same secret door twice but doesn’t explicitly state it.
Swords & Wizardry - 2008
I’m reading Complete: Revised which released in 2023. Other versions of S&W (white box, fmag, etc) are faithful to OD&D.
Secret Doors: When the characters search a 10-foot area for one turn, each character has a 2-in-6 chance to find a secret door if there is one. Elves, however, have a 4-in-6 chance to find it and a 1-in-6 chance to notice it without ever searching. Finding a secret door does not necessarily mean the characters know how to open it; they just know that it is there.
For reasons unclear to me, S&W nerfs the Elf’s passive perception in OD&D from 2-in-6 to 1-in-6. Otherwise, it’s faithful to OD&D.
Bonus points for including an example of play that applies its own rules correctly and consistently:
Russell: “Okay, I check inside the pit for secret doors.”
Referee: “It takes you a full turn to check a 10-by-10 area for secret doors. Which wall are you searching?” The Referee knows that there is actually a secret door in the floor of the pit, but is careful not to reveal anything by specifically mentioning the floor.
Russell: “North wall and the floor.”
Referee: “That will take two turns.” He rolls two six-sided dice in the first turn, when Eyeballs is checking the north wall of the pit. Even though he knows there is no secret door, he rolls a die anyway.
If he didn’t, the players would know for sure that there was no secret door. The second die roll is a check for wandering monsters, because the party is using a full turn of time to search. “Nothing happens in the first turn, and you don’t find a secret door in the north wall. You start searching the floor of the pit.” Once again, the Referee checks for wandering monsters, but still doesn’t roll a 1. He rolls 1d6 to see if Eyeballs finds the secret door, and now he rolls a 1, meaning that the secret door is found.
Referee: “You discover that the crack between the floor and the walls goes in really deep. You think that the floor might swing downward like a trapdoor. You also find what looks like a keyhole in the floor, in the northwest corner.”
LotFP - 2010
Searching
Many items and features of interest are hidden from open view, with secret doors or compartments being the classic example. To find these things, characters must search for them. Under normal conditions, searching takes one turn per character per 10’ of area searched. Hidden items or features have a base 1 in 6 chance of being found per turn of searching. The Referee may create hidden elements that are more difficult (or easier) to detect at his discretion, and some class abilities will affect this.
Dwarves and Elves bump this up to 2-in-6, and the Thief class (called Specialist) can spend their points on improving, all the way up to 35-in-36 (only fail on boxcars on 2d6). I like LotFP’s thief a lot.
ACKs 1e - 2012
Some doors are somehow concealed or hidden - these are secret doors. Common secret doors are sliding panels in a wall, trap-doors under rugs, and so on.
Secret doors can only be spotted if characters are specifically looking for them. When a player declares that his character is looking for secret door, the Judge should make a proficiency throw on behalf of the character. All characters except elves will spot a secret door if one is present on a throw of 18+ on 1d20. Elves have keen eyes that allow them to detect hidden and secret doors with a proficiency throw of 8+ on 1d20 when actively searching, or 14+ on casual inspection.
It takes 1 turn for a character to search a 10' x 10' area. Since the Judge rolls the dice, the player never know if the roll failed or if there simply is no door in the area searched. Each character has only one chance to find each secret door.
…
Alertness: The character gains a +4 bonus on any proficiency throws to hear noises and detect secret doors. With a proficiency throw of 18+ he can notice secret doors with just casual observation. He gains a +1 bonus to avoid surprise.
This is effectively how OD&D works with the probabilities halved (1-in-6 is 16.66%, 18+ is 15%, 2-in-6 is 33.33% 14+ is 35%). Relative to B/X (which ACKs is based on, broadly), Elves regain their passive perception (and non-elves can have have passive perception with the Alertness proficiency) and are juiced up to OD&D levels (2-in-6 passive, 4-in-6 active).
ACKs 1e is explicit in that you can only try to find a secret door once per character.
Hyperborea 2e - 2017
Doors: Doors are oft encountered when exploring dungeons, castles, towers, and the like. They are sometimes stuck, locked, or cleverly hidden.
Concealed Doors: These are doors obstructed by something else; e.g., behind a bookshelf, a tapestry, or a stack of barrels. They can be found as secret doors are (q.v.), unless the player specifically states his character is looking behind the noted obstruction, in which case the concealed door will be revealed automatically.
[…]
Secret Doors: Any man can search for and locate a secret door on a 2-in-6 chance. Some classes are better suited to detection, such as the thief, who enjoys a base 3-in-6 chance of success. Such checks should be rolled secretly by the referee. Searching for a secret door typically requires 1 turn (10 minutes) per 10 × 10-foot area to ensure a thorough examination.
This is one of the ways that Hyperborea departs from AD&D 1e, preferring the OD&D base probabilities (2-in-6 instead of 1-in-6) and time scales (1 turn instead of 1 round). The text is not clear on if repeat searches are allowed.
Hyperborea is a humanocentric setting (no elves), and so thieves instead are given the boost (though not to the level of OD&D’s elves: 3-in-6 instead of 4-in-6).
Old School Essentials - 2019
Searching for Secret Doors
Some doors are hidden or concealed. Adventurers may choose to search a 10’ × 10’ area for secret doors. See Searching.
Chance of finding: If a character is searching in the right location, there is a 1-in-6 chance of finding a secret door. (Some types of adventurers may have an increased chance.)
[…]
Searching
The following stipulations apply to searching for secret doors, room traps, and treasure traps.
Time: Searching takes one turn.
Referee rolls: The referee should always roll for the character searching, so that the player does not know if the roll failed or if there are simply no hidden features present.
One chance: Each character can only make one attempt to search a specific area or item.
Faithful to BX.
Simulacrum - 2021
Simulacrum replaces Intelligence, Wisdom, and Charisma with Perception, Willpower, and Arcana, modifiers use the same ranges as BX, but the standard is to use 4d6-keep-highest-3 instead of 3d6 for stat distribution, so characters tend to have slightly higher modifiers than BX.
Spotting Secret Doors
Spotting a secret door is a Perception check (see p. 24), with the difficulty based on how well the door is concealed. During cautious exploration (see p. 27), a separate group check (see p. 20) is made automatically (by the GM, in secret) for each secret door within 10 feet.
A character can also actively search a 10 ft × 10 ft square for secret doors. This takes 10 minutes; more than one person cannot search the same square at any one time.
Spotting the average secret door is Very Hard (17+) during cautious exploration, and Daunting (11+) via an active search. Finding one does not necessarily reveal how it opens.
Everyone’s an elf! Perception checks are d20+perception mod, roll at least the given number. So, everyone has an average of a 20% chance to notice a secret door while walking past it, and a 50% chance to find it if they’re actively searching for it.
Simple, easy to run, no funny business.
Hyperborea 3e - 2022
DOORS
Doors are oft encountered when exploring dungeons, castles, towers, and the like. They are sometimes stuck, locked, or cleverly hidden.
Concealed Doors: Obstructed doors; e.g., behind a bookshelf, a tapestry, or a stack of barrels. Found as secret doors, unless a player specifically states that their character is looking behind the noted obstruction, in which case the concealed door is revealed automatically.
Secret Doors: Any character can search for and locate a secret door on a 2-in-6 chance. Some classes are better suited to detection, such as the thief, who enjoys a base 3-in-6 chance of success. Such checks should be rolled secretly by the referee. Searching for a secret door typically requires 1 turn (10 minutes) per 10 × 10-foot area to ensure a thorough examination. A hurried attempt may yield a decreased chance-in-six.
This works exactly the same as in Hyperborea 2e, with an unelaborated line that you can trade speed for reduced chances (though never providing further guidance).
ACKs 2e - 2024
Some doors are somehow concealed or hidden — these are secret doors. Common secret doors are sliding panels in a wall, trap- doors under rugs, and so on. Secret doors can only be discovered by searching (see above). Apart from being hidden, secret doors function like other doors, and might need to be unlocked, battered down, or bashed open.
This refers us to a table:
All characters have the “Adventuring” proficiency. Other relevant proficiencies are “Alertness” (+4 to searching with Adventuring, or +2 if you also have “Searching” proficiency) and “Searching”, which is not listed in the proficiency list but instead a thief class ability (calling everything a proficiency is a quirk of ACKs) and gives you a level-dependent success rate (just like how hear noise works in 1e or BX).
So 1st level Thieves get the default 18+. ACKs 2e splits up searching into “hasty” (can be done while moving, or in 1 round) which is only permitted to Thieves, and “methodical”, which takes the full turn. Methodical searches are effectively the same as ACKs 1e and BX, searching a 10x10ft area, taking a turn, and working ~1/6th of the time. Rather than Elves being better at searching, ACKs makes thieves better at searching, giving them a +4 (ie, 2-in-6 at 1st level).
Meanwhile, OD&D’s elven passive perception is also shifted to the thief and rebranded as “hasty” searching.
It’s a coherent system that works well at the table, plagued by the relevant information being spread across hundreds of pages and multiple definitions with overloaded terms.
Dolmenwood - 2024
Secret Doors
Whether cunningly integrated into stonework or concealed beneath a blanket of moss, some doors cannot be seen by casual observation. Searching for secret doors is discussed under Hidden Features, p152.
…
Hidden Features in Dungeons
In enclosed spaces, hidden features can often be located by narrative interaction (p150). Alternatively, players may declare that they are searching a certain object or 10′ × 10′ area for hidden features (e.g. traps, secret doors, hidden compartments, etc.). The Referee rolls a Search Check.
Time: Each search takes 1 Turn.
Multiple characters: If space permits, multiple characters may search the same object or area. Up to 3 characters can simultaneously search a 10′ × 10′ area.
Retrying: Characters may search the same object or area again as often as they wish, each attempt requiring an additional Turn.
Referee rolls: The Referee rolls all Search Checks, so that players do not know if the roll failed or if there are simply no hidden features present.
…
Narrative Interaction
The basic game procedure (p138) serves as the fundamental means of interacting with hazards and challenges. The environment is described and clarified with questions from the group, then the characters act and the Referee judges what happens. Sometimes a die roll is required—putting a character’s fate in the hands of chance—but it is often possible to bypass hazards using ingenuity, without any kind of random roll.
Example: Exploring a cave system of crystal-encrusted grottoes, the party comes across a 10′ wide chasm blocking their path. The players ask the Referee if they can jump across. Consulting the rules for jumping (p153), the Referee says that a Strength Check is required. Not liking the odds, the players discuss other approaches. Could the large statue they previously encountered be dragged here and tipped across the chasm as a bridge? Could they attach a rope and grappling hook to rocks on the other side and swing across?
…
Skill Checks
Skills represent specific competencies practiced by adventurers. All adventurers can use the Listen, Search, and Survival skills, and some Classes grant the use of additional, specialised skills.
Rolling: Roll 1d6 and add any situational modifiers. If the result equals or exceeds the character’s Skill Target for the skill being tested, the check succeeds. Skills default to a target of 6, unless the character’s Kindred or Class specifies a lower target.
1s and 6s: A roll of natural 1 always fails and a roll of natural 6 always succeeds, irrespective of modifiers.
Kindred and Class: In cases where a Kindred and Class grant an improved chance of success with a skill (i.e. a lower Skill Target), use the more favourable.
When to Roll a Skill Check
Each skill applies in certain specific situations, when called for in the rules.
Listen Checks: Rolled when a character presses their ear to a door to detect the presence of creatures on the other side (see Listening at Doors, p151).
Search Checks: Rolled when searching for secret doors or traps (see Hidden Features, p152).
Survival Checks: Rolled when trying to find food in the wild (see Finding Food in the Wild, p152).
This a lot of referencing, but we got there in the end. We’re rolling a d6 and generally trying to get a 6+, so this is a 1-in-6 check. Elves only need a 5+ (so 2-in-6). As a departure from BX, you can explicitly try to find the same hidden door as many times as you’d like. There’s direct guidance for how many characters can simultaneously search the same 10x10ft area.
Of note, the Narrative Interaction section is a very good description of what I think of as prototypical OSR play, explained clearly in the PHB (rather than in the DMG like in 1e). You can roll dice, but the odds aren’t good and the risks can be high, maybe it’s better to come up with a different way. This is on the short list of things I include in my “teach” when I’m onboarding a new player to the table.
Summary
I marked the cells in orange where I felt like a derived game was deviating from its source material.
OD&D → Seven voyages of Zylarthen, Swords and Wizardry
AD&D 1e → OSRIC, Hyperborea
B/X → Rules Cyclopedia, Basic Fantasy, Lamentations, OSE, Dolmenwood
Conclusions
On a game design level, I think the differences in time and probability comes down to how frequently we want players to find secret doors. The better the chances and the shorter it takes, the more we encourage players to say “I search for secret doors” without any cause to believe there might be some here.
Of the listed games, the most extreme here is AD&D 1e. You can search 10x as quickly as in any of the other games, and if the GM interprets the text as allowing players to search again when they fail, then searching the same 10x10ft area for 10 consecutive rounds gives a 5-in-6 chance to find a secret door, so it’s by far the most generous with its searching rules.
Some unlisted newer games (Knave, Shadowdark) grant automatic success if the players are searching in the right spot. I like this superficially, but I find it collapses the gradient of solutions. In AD&D 1e, if you strongly suspect that a door is in a spot, search, and don’t find it, you can do something else. You might use your Wand of Secret Door & Trap Location or spend a spell slot on Knock (which works on undiscovered secret doors, unlike the BX version). You might go as far as to excavate.
These, to me, are interesting options that become obsolete when the simple solution (just look at the wall) always works.
The other main divide is if we want passive detection or not. Gygax did, which is why it’s in OD&D and D&D 1e. In my experience, the OD&D/1e approach of flat chances (2-in-6 or 1-in-6 respectively) works a lot better than the ACKs approach of level-and-feat dependent chances where now I have to maintain more state on my tracking sheet that tells me what people’s passive perception is.
Overall, if I were to advocate for an approach, I’d go with AD&D 1e’s implementation. I prefer the rates (1000sqft in 10m rather than 100), and if you want to concentrate on the same area, you get implied better chances (you only fail a 1-in-6 10x in a row 1/6th of the time).