Lock bypass

Lock bypass is one of the most important parts of locksmithing, especially with respect to public buildings which must be able to be opened from inside in case of fire, thus allowing the use of "letter box tools" among other techniques.

Padlocks may be bypassed by shimming, where one inserts a sprung steel device to retract the spring-loaded catch that restrains the shackle.

The previous method may be assisted by gently prying the door from the frame with an air wedge or lever.

To avoid bypass, a door should be secured using a deadbolt system, in which the locking mechanism and bolt are operated by the key.

This prevents the device from being opened without the locking mechanism itself being properly operated.