Lock bumping is a lock picking technique for opening a pin tumbler lock using a specially crafted bump key, rapping key or a 999 key. A bump key must correspond to the target lock in order to function correctly.

History

A US patent first appears in 1928 by H. R. Simpson called a rapping key. In the 1970s, locksmiths in Denmark shared a technique for knocking on a lock cylinder while applying slight pressure to the back of the lock plug. When the pins would jump the inside of the cylinder, the plug would be able to slide out freely, thus enabling the locksmith to disassemble the lock quickly. The use of a bump key was not introduced until some time later and was first recognized as a potential security problem around 2002–2003 by Klaus Noch, who brought it to the attention of the German media. After further examination of the procedure, a white paper was drafted in 2005 by Barry Wels & Rop Gonggrijp of The Open Organization Of Lockpickers (TOOOL) detailing the method and its applicability. A patent exists for a lock device following the same principle as the bump key from 1926–1928.