If the lock has identifying code numbers, they are used as a guide for cutting and notching a key blank to make a new key. New keys are also made from impressions which are made by placing a key blank into the lock. By following marks left on the blank, notches are filed on the blank until it opens the lock. Combination locks, such as those on safes, are sometimes opened by touch, that is, by rotating the dial, and listening for contact points when the wheels come into place. If this fails, a hole may have to be drilled through the lock to open it.
Locksmiths also fix damaged locks.
Increasingly, Locksmiths are developing and maintaining security systems for customers. Re-keying is changing the tumblers of a lock to fit a new key. In a master key system, some keys must open all doors, others open several doors, while some keys open individual doors. In some hotels and other lodging places, Locksmiths install security systems that require an electronic key card to open guest room doors. Some Locksmiths install and repair electronic burglar alarms and surveillance systems that signal police or firefighters when break-ins or fires occur.