Chisels

A thief may attempt to force a lock open with a lock chisel and a small hammer. This is not really a highly skilled activity, and the DM might consider extending this to non-thieves. The base chance for success is equal to the open doors percentage (which is Strength-based, of course). A thief may add one-fifth of his open locks chance to this base chance—knowing something about locks does give a slight advantage here. Obviously, forcing a lock is a noisy activity and any hope of subtlety and surprise evaporates with the first blow.