key-per the smart comments coming
seriously?, try another key that fits the lock and whilst putting the key in
and out very slowly, try to maintain pressure in the direction of opening
the lock. This attempts to move and keep the lock pins from passing back
over the shear line, thus opening the lock.
Failing that, try a small screwdriver and gently wedge it in the bottom of
the lock whilst using a flattened out paperclip with one end turned up
slightly (about 2 mm) to move the lock pins. Use the screwdriver as a "key"
try to maintain pressure on the lock in the opening direction whilst
pulling/pushing the paper clip in an out whilst trying to get the "feel" of
the pins and whether or not they have passed the shear line.
If neither of the above work, either invest in a set of good lock picks or
pick up a brick
If anyone asks "can i pick locks", the answer is no! ;-)
If anyone else asks if i can pick locks, i can tell you but then i would
have to kill you :-[
If you live near me (merseyside) then pick me up and i'll open it up for you
whilst you are acting as a lookout ;-)
If you want to google for the e-book "MIT guide to lockpicking" it may help
wolfie