If there's one thing the OSR community can debate until the heat death of the universe it's skill systems. Some people hate them and want none of them, some people like something simple, most people agree that the 3rd edition onward have too much crunch.

Every new OSR game seems to have its own system bolted on top. When I talk about skill systems in B/X, some of you might imagine I'm talking about the ability check system presented in OSE as follows:

Ability Checks
The referee may use a character’s ability scores to determine the character’s chance of succeeding at various challenging tasks.
Rolling an ability check: The player rolls 1d20 and, if the result is less than or equal to the ability, the check succeeds. If the roll is greater than the ability, the check fails.
Modifiers: Bonuses or penalties to the roll may be applied, depending on the difficulty of the task. A modifier of –4 would be a relatively easy ability check, and a +4 would be very difficult.
1s and 20s: An unmodified roll of 1 should be treated as a success and a 20 treated as a failure.

This is actually not what I'm talking about, though it's likely more familiar to modern D&D players than the actual skill system underpinning D&D.

No, the first place we see the skill system I'm talking about is somewhere else entirely, and that's what we're going to be diving into today.

Open doors: The chance of success with attempts to force open a stuck door.

It ranges from a 1-in-6 chance to a 5-in-6 chance. These X-in-6 skills can be found all over the place, and are generally universal (with some apparent exceptions I'll talk about in a bit).

Listening at Doors
Chance of success: PCs have a 1-in-6 chance of detecting subtle sounds beyond a door. (Some types of adventurers may have an increased chance of success.)

Those some types of adventurers are generally the demi-humans, but this is another universal skill. Next up:

Chance of success: If a character is searching in the right location, there is a base 1-in-6 chance of finding a secret door or room trap. (Some types of adventurers may have an increased chance.)

Again, benefit to the demihuman, again, a universal skill

Chance of triggering: Every time a character makes an action that could trigger a trap, there is a 2-in-6 chance of the trap being sprung.

Another universal, this time it's a bit less clear. Lets rephrase this as a 4-in-6 chance to avoid a trap. We can think of this as being a kind of luck skill. Or we could leave this one off entirely, it's a lot less clear what the implication is. Obviously some triggering mechanisms probably have a 100% chance (pulling a lever).

Foraging for herbs, fruits, nuts, etc. can be performed alongside normal movement (see Overland Travel). The party has a 1-in-6 chance per day of finding enough food for 1d6 human-sized beings.

A forage skill, lovely. This ones interesting as it is a 'whole party skill' rather than an 'individual' skill. I'll talk more about why this doesn't matter later.

Hunting must be engaged in as the sole activity for a day—no travelling or resting is possible. When hunting, there is a 1-in-6 chance of encountering animals which may be suitable for eating (if they can be caught!). This is in addition to the normal chance of random encounters (see Wa n-dering Monsters).

And hunting works the same as Foraging, but is higher effort on the players part

Losing Direction
At the start of each day of travel, the ref-eree should roll to determine if the group loses direction. The probability depends on the terrain being traversed:
▶ Clear, grasslands: 1-in-6.
▶ Barren lands, hills, mountains, woods: 2-in-6.
▶ Desert, jungle, swamp: 3-in-6.

Lets restate this one as a navigate skill with a chance depending on the type of terrain. 5-in-6, 4-in-6, or 3-in-6 depending on the difficulty of the terrain. Listed later is the fact it's 4-in-6 to navigate while waterborne. Paths and rivers eliminate this chance. While waterborne however, it requires a specific navigator to help sail, so this is clearly not a skill that all adventurers have.

Forceful boarding: If the occupants of one vehicle wish to forcefully board the other vehicle, there is a 2-in-6 chance of being able to successfully manoeuvre the vehicle into a boarding position. The two vehicles may then be clamped together with grappling hooks.

That ones a lot nicher, but it's there. The final one isn't written using the X-in-6 wording but it might as well be.

Surprise Checks
Each side that is not already aware of the other’s presence rolls 1d6.
Monsters: The referee rolls for monsters.
PCs: One player rolls for the adventuring party as a whole.
Results: A result of 1 or 2 means the side is surprised.

That's a 2-in-6 stealth check right there.

Now lets hop on over to the classic fantasy genre rules, and see what we can find in there.

Tinder box: Used to light fires, including torches. Using a tinder box takes one round. There is a 2-in-6 chance of success per round.

Tinder boxes, a bit odd, 'light fire' skill I suppose.

Detect Construction Tricks
As expert miners, dwarves have a 2-in-6 chance of being able to detect new construction, sliding walls, or sloping passages when searching.
Detect Room Traps
Due to their expertise with construction, dwarves have a 2-in-6 chance of detecting non-magical room traps when search-ing (see Dungeon Adventuring in Core Rules).
Listening at Doors
Dwarves have a 2-in-6 chance of hearing noises (see Dungeon Adventuring in Core Rules).
Detect Secret Doors
Elves have keen eyes that allow them, when actively searching, to detect hidden and secret doors with a 2-in-6 chance (see Dungeon Adventuring in Core Rules).
Listening at Doors
Elves have a 2-in-6 chance of hearing noises (see Dungeon Adventuring in Core Rules).

All the demihumans have notes that essentially improve their search and listen skills.

And now, we run into our first properly curious case.

In dungeons, a halfling can hide in shadows or behind other forms of cover. The chance of success is 2-in-6. Hiding requires the halfling to be motionless.
Listening at Doors
Halflings have a 2-in-6 chance of hearing noises (see Dungeon Adventuring in Core Rules).

We established earlier that everyone essentially has a base 2-in-6 chance as a party to successfully be stealthy. This is exactly the same as the halflings stealth. However, theirs enables an additional layer of stealth on top of the base one. If they are still, and behind cover or in shadow, they have an extra chance to be unnoticed to the rest of the party. This enables situations where the entire party is noticed apart from their more stealthy halfling. This is also how I run the thiefs move silently and hide in shadows abilities, and the halflings other hide in woods or undgrowth. It's curious that those other abilities aren't rated X-in-6 and instead have percentages however.

They also have a better listen skill, but curiously not a better search skill.

Finally, the thief introduces one more spanner in the works with their hear noise ability.

Thief Skills
▶ Hear noise (HN): In a quiet environ-ment (e.g. not in combat), a thief may attempt to listen at a door or to hear the sounds of something (e.g. a wandering monster) approaching.

I think we can treat this as an enhancement to the listen skill, like with the demi-humans, that improves as the thief gains experience.

Last off, I know this isn't pure B/X, but for completeness let's take a look at OSE Advanced Fantasy Genre Rules.

Foraging and Hunting
A party with a barbarian succeeds at foraging with a 2-in-6 chance and finds prey when hunting with a 5-in-6 chance (see Wilderness Adventuring in Core Rules).

And this is where the group skill check nature of stealth get's resolved. Forage and Hunt are also group activities, but being led by a barbarian enables far better success rates. We can treat the implied stealth check of the surprise rules the same way, the party works together and is beholdant to the ability of their stealthiest member showing others where to walk and stopping the parties movement at just the right time.

From 2nd level, a bard has a 2-in-6 chance of knowing lore pertaining to monsters, magic items, or heroes of folk-tale or legend. This ability may be used to identify the nature and powers of magic items.

Not a universal skill by any means, I personally think as such this one feels more like waterborne navigating. Perhaps it should have been left up to a % roll instead of an X-in-6. Alternatively, you could make lore a universal skill, and give everyone a 1-in-6, letting bards have a better chance to have knowlewdge and gaining the enhancement of identifying magic items.

I'm not going to list them all out, but the demihumans have the search and listen enhancements you've probably come to expect by now.

A party with a druid has only a 1-in-6 chance of getting lost in woodlands. See Wilderness Adventuring in Core Rules.

Druids score themselves a 5-in-6 in the skill we now have a name for, pathfinding.

Underground, duergars have a 3-in-6 chance of moving silently.

Another halfling style enhancement to their stealth aka make the enemy surprised check. Or perhaps the duergar should lead others to also have a 3-in-6 chance of surprising the enemies. I suppose if I ever end up with a duergar in a party of mine I'll have to make that decision.

Gnomes have the same halflign 2-in-6 small person bonus hiding too. I'm not going to list it all out again.

Foraging and Hunting
A party with a ranger succeeds at forag-ing with a 2-in-6 chance and finds prey when hunting with a 5-in-6 chance (see Wilderness Adventuring in Core Rules
Surprise Attack
In the wilderness, a ranger has a 3-in-6 chance of going unnoticed when sneaking up on a target. If the ranger goes unno-ticed, the target may be surprised (see Surprise under Encounters in Core Rules)

The same improvement to foraging and hunting that the barbarian got, but an additional improvement to stealth. Again, this ones a toss up between it being an additional individual check, or improving the parties stealth as a whole.

Blend into Stone
Svirfneblins have the uncanny ability to go unnoticed when in an environment of natural or carved stone so long as they remain silent and motionless. The chance of success is 4-in-6 in gloomy conditions or 2-in-6 in well-lit conditions.
Stone Murmurs
Svirfneblins can understand the imper-ceptible grumblings of stone. If a svirf-neblin stands quietly for one turn with their ear pressed against a stone surface, they have a 2-in-6 chance of divining one of the following pieces of information (player’s choice):
▶ The presence of secret doors in the stone, within 10’.
▶ The presence of gems or precious met-als, up to 30’ beyond the surface.
▶ The presence of living creatures, up to 30’ beyond the surface.
▶ The presence of bodies of water or open spaces, up to 60’ beyond the surface.

A stealth improvement for the svirfneblins. This one I'd stack on top of their base always, and probably not let lead a party in this fashion as it seems much less knowledge based and much more innate to their race. They also have a stone murmers ability, which is really strange and I don't know how to interpret. Clearly it's not a universal skill however, so I'd suggest again this one might have suited 33% more than 2-in-6.

So, that's my round up of all the X-in-6 universal skills that underpin B/X D&D. I think they can be broadly broken down into the following:

Individual Skills

Inidividual skills are rolled for every person attempting an activity.

  • Force is used for forcing open doors through strength.
  • Listen is used to hear monsters through doors (breaking their stealth).
  • Search is used to find hidden passages and traps.
  • Luck is used to not trigger traps by through chance by stepping over a pressure plate instead of on it.
  • Enhanced Stealth is used when the party fails its stealth check, but you are a class that has better odds of hiding.
  • Use a tinderbox is used to use a tinderbox.

Group Skills

Group skills are performed by the entire group, usually with a single person leading the activity who can provide their experience as a bonus to everyone.

  • Forage is used to find food while travelling overland.
  • Hunt is used to find food dedicating time to the task.
  • Pathfind is used to navigate without a road or river.
  • Board is used to position vehicles for boarding.
  • Stealth is used to be unnoticed by foes.