Everyday locks, such as those found on office mailboxes and cabinets, get a lot of use. The more use a lock gets, the more important it is to have that lock functioning properly. Changing the locks on a mailbox or cabinet is similar to changing the lock on a door, with a few important differences. The largest difference is usually in the mechanics of the lock. Where a door lock usually retracts a bolt to open, the plug of the key in most mailboxes and cabinets is fixed to a bar that rotates with the key turn.