When we first saw the videos about lock bumping, we found it to be disturbing, because it is so easy to make bump keys and the information is readily available on the Internet.
More than 90% of the locks currently securing American homes are susceptible to being opened in less than one minute using a modified key using a technique that has been around since the 1970s. Danish locksmiths originally discovered the technique that works best with standard pin tumbler type locks, which happen to be the most common type of locks using in homes.
Pin tumbler locks use double sets of spring-loaded pins that align with the circumference of a lock cylinder when the proper key is inserted. The pins are different lengths and normally require a key with valleys of the proper depth for the lock to be opened. The lock cylinder cannot be turned until the pins line up with the surface of the cylinder. When the pins align, the lock can be opened.
A bump key is simply a standard key that has been cut with evenly spaced valleys cut to a certain depth. Every valley is the same depth. The key is inserted and tapped with a small hammer or mallet while keeping a slight turning pressure on the key. The idea is to tap the key so that angles on the valleys bump up gently against the pins, which causes them to bounce. The slight pressure on the key causes the keys to stick in the open position and the cylinder can be turned.
This You Tube news broadcast video demonstrates the technique.
The real problem is that there are dozens of videos and other information on the Internet that teaches anyone how to make bump keys. All it takes is a key, a file and about 10 minutes. The videos make this look so easy that it is scary.