<if you can find the black-background version of the same size and quality as the above, then use that>

    It is done by picking with tools and by cleverness,
    plus knowledge and study of such items.

Q: Do nonthief characters have any
chance to open locked chests or
doors?

A: Only thieves can pick locks in the AD&D
game. Other characters can try to force
locked closures by making an open doors
attempt or bend bars/lift gates roll, as per
the PH, page 9. It is up to
the DM to decide when and how a locked
door or chest can be opened.
(144.6)

Opening Locks may be attempted by any given thief but once per lock.

If the score generated exceeds the adjusted (for ability and race) base
score, the thief has failed; and no amount of trying will ever enable him or
her to succeed with that lock, although the thief may try again when he or
she has risen to a higher level of experience. Success opens the lock.

DMG:

Opening Locks:

The act of picking the lock to be opened can take from 1-10 rounds, depending on the complexity of the lock.
As a rule, most locks will take but 1-4 rounds of time to pick.

<30 points of damage will break open a padlock: T1-4.72>
<another example, 25 points will break a padlock: T1-4.81>
<another example, 30 points of damage will break open a lock: T1-4.49>
<another example, 35 points of damage will break open a lock: T1-4.52>
<condense the above>

<
LTH (The Thief: A special look, d47, bd5)
Opening locks, as we all know, is a
matter of “cleverness, plus knowledge
and study of such items” (PH, page 27).
Again, stupid thieves could be penalized, but likely that would be going too
far and players would rebel. However,
real Intelligence does come into play on
puzzle locks and complex closures. Nothing forbids the inclusion of “complex
 locks” in addition to the RUN-OF-THE-MILL,
crude lock the thief will run into most of
the time. “Complex locks” can subtract
some set amount from the thief’s percent
chance to open the lock, cutting his
chance by a 1/3, 1/2, 2./3 or even
more for truly unusual, challenging closures. Such complex locks should be
expensive and rare. Picking a complex
lock (or an ordinary one) in stress situations (practice does not count) can give
a thief actual experience, if the DM
chooses to award experience for such an
act. An ordinary lock takes 1-4 rounds to
open; a complex one can take 1-10
rounds (as suggested in the DMG, page
19) or perhaps even longer for unique
ones.
>