Move Silently

[Falstaff]

How do you adjudicate non-thieves attempting to Move Silently, or Hide? I've got no issues with the other thief skills, but these two are problematic. I'll explain.

I've been told the thief skill Climb Walls, is almost supernatural in its execution, allowing the thief (only) to climb sheer surfaces that have little to no handholds. Fair enough. I imagine the thief climbing the alabaster tower that has an almost glass-like surface. Pretty cool. I just go ahead and have non-thieves make some sort of roll to see if they can climb walls (but they can't even attempt to climb the sorts of walls the thief can). All good.

With Move Silently and Hide, I've heard said they too are also almost supernatural in execution. Like, the thief can move and literally not make a sound and can hide, almost in plain sight. Non-thieves cannot do this, but they should be able to move silently and hide, to some extent.

Here's an example:

It's dark, and a 5th level thief tries to move silently through a camp of enemy soldiers. They have a 45% chance to do so.

It's dark, and a 1st level cleric tries to move silently through a camp of enemy soldiers. What chance do they have? What do I roll? I've decided as DM the cleric (or fighter, or magic-user for that matter) should be able to attempt it, but how do I rule this?

If I have them make a Dexterity roll vs a difficulty of 17 (as per the optional rules on page 153), that gives them a 35% chance - and that's with Dexterity 18 (it drops to 20% with no Dexterity modifier). That seems very harsh. They aren't bumbling dolts. Yet, if I think they should have a pretty good chance of sneaking through a camp at dark, the very most I can offer is a 45% chance - which equals a 5th level thief.

I'm pretty much stymied here.

[CptClyde]

Maybe we can look at it this way: the thief gets his MoveSilently value when others basically have a 0% chance at success. So in a situation where it is possible for the cleric, then add that percentage to the theif's chances.
I have in the past said "okay, it would be possible for you to sneak past this guard but not easy. Roll a 1 on a d6. " That's about a 17% chance. I'll then allow the thief a +17% to his ability. (Using the optional ability roll table you referenced is a better idea though than my 1d6 example)

[Seven]

Normally, armor has a lot to do with it.
Chain and plate mail are noisy.
The type of boots matter also.
The thief is wearing leather boots without heels, basically slippers and he walks flat-footed--most everybody walked like that in the middle ages as general footwear were often similar to socks.
The fighters are wearing stronger boots and hit the ground heel first, if geared for combat.

There is probably an argument that a Magic-User should have a decent chance of walking silently, but would probably move very slowly when doing so.

[Dimirag]

Hiding for thieves lets them to hide on dark corners or other places where a non-thieves would be easily detected but the chance of them to be detected still exists.
Non-thieves characters require a good hiding spot (behind a statue, inside a wardrobe, etc.) with also a chance to be detected.

Moving Silently allows a Thief to reduce the chances of being heard while non-thieves have the "base" chance, maybe more based on equipment.

Moving thru dark places does not use Hide rolls, but can use Move Silently rolls if the Thief is being sneaky as they tend to be.

Now, what is the "base" of being detected? I would use a 1 in 6, for Hiding rolled when the npc is searching, for MS rolled when the pc is moving (in case of a Thief with a successful MS roll I would use a 1 in 12 chances, effectively cutting his chances of being detected by half).

There is also another approach where a Thief's successful roll cancel the chances of being heard or found, this is faster but if applied to opponents NPC they can become quite deadly.