These are a couple of bits from my Version 1 of 5 Stones Rules.
This is pertaining to Rogue (and yes I use Rogue not thief,) class abilities Lock Picking and how they work, the additional "critical" rules will be explained in another post.
The rules below are inspired by Philotomy's Musings , Delta's D&D
and Real Life, more or less.
D&D Locks are not true medieval locks which served mainly to stop crimes of opportunity. They more closely resemble later 17-18th century locks which require a bit of skill to pick.
However lock picking is not that hard of you have the time. A regular Joe can open many inexpensive modern locks such as a bicycle lock with improvised tools and a bit of luck and these would be harder to open that D&D locks.
To make lock picking more useful in game , more fun and more realistic I do the following.
To pick a lock open a character needs Thieves or Locksmiths Tools and the Open Locks Class Ability.
A single attempt takes 1 minute (this rule taken from GURPS for lack of better data and the fact it fits neatly being either 1, 6 or 10 rounds)
If it is a critical success the lock is opened as if a key is used. On a critical failure roll 1d6, 1-2 nothing 3-4 lock jammed 5-6 picks damaged. Damaged picks or tools are at -10 to all rolls as are improvised ones and being damaged again ruins them.
Superior Picks or Tools may be available and add a +10 to all rolls. Picks damaged results render the picks "normal" . Magic versions of these may exist with different effects however in general they can ignore picks damaged results
If a roll to pick locks is an ordinary failure, the player may roll again with one round per attempt until they either succeed or critically fail.
Note that some locks are easier to open gaining a bonus to rolls and others more difficult than normal and may inflict a penalty on attempts.
If the net chance is zero or less, its beyond the ability of the character. This will be known with one attempt, roll normally than inform the player the lock cannot be picked at that skill level. Also some locks are designed to trigger if picking attempts are made. Such locks open as per normal but any failed attempt renders the lock unpickable. These can stack with each other. If the net chance is 100% or greater, roll as normal but any result other than a critical success opens the lock.
Any rogue with over 100 in open locks may make one attempt to open a magical locks at skill-100.