Insert the matching key into the lock. The matching key is the one with numbers engraved on it.
Turn the key clockwise.
Open the drawer you need. If your file system has two drawers, one above the other, both drawers lock and unlock when you turn the key in the lock.
Close the drawer once you've retrieved your file. Both drawers must be closed completely to lock the cabinet again.
Turn the key counterclockwise to lock the drawers. Remove the key.
Insert the matching key into the lock and turn it clockwise. Remove the key from the lock.
Insert the lock removal key into the lock. The lock removal key looks like the matching key, but has no numbers engraved on it.
Turn the lock removal key clockwise a quarter turn.
Pull the key straight out. The lock will come with it.
Replace the lock with a new lock.