Bump Keys / Hammers

BUMP IT -- A Faster, Easier and Ridiculously Efficient Way to Defeat Pin Tumbler Locks

Bump Keys are one of the most basic locksmith tools around, consisting of key blanks that have been cut down to the deepest increments in each position. The Bump Key thus formed is used to assist the Locksmith in employing a version of the percussion technique in which a Bump Hammer is used to rap the bow of the partially inserted bumpkey while a small amount of turning tension is applied simultaneously.

We've produced a Kindle book that is a great bump key instructional piece.  It also approaches the subject from the opposite side and explains in plain, simple terms how homeowners can absolutely prevent lock bumping.  Check out "Don't Bump My Lock", just click any word in this sentence.