How prevalent is "key bumping," and how concerned
should one be about it?
A "999" or bump key
can be any key that fits a particular pin tumbler lock and that has been
modified so that all of its cuts (or grooves) are made to the deepest
allowable position as defined by each manufacturer. The term "fit" means
that the key will enter the keyway (the front of the lock) but will not
For example, assume all of the locks in a particular apartment
complex are produced by the same manufacturer and have the same keyway.
The key for apartment 101 can enter the lock of
apartment 207 (or any other apartment) but will only
unlock the apartment for which it was cut (i.e., apartment
101). Any key cut for any apartment in this example could be
modified to act as a bump key and then could be used to open any other
apartment within the complex (or potentially any other complexes where the
same manufacturer's locks were installed).
The term "bumping"
refers to the process of forcing the key to interact with the pin tumblers
by "bumping" or rapping it with a plastic mallet while it is inserted into
the lock. This process entails hitting the head of the key, causing it to
rapidly move forward. When the key is struck correctly, each of the bottom
pins is "bumped" upward for a brief instant, thus allowing the lock to be