on every home and business in the world, is the pin-and-tumbler lock. To understand how lock bumping works, it helps to understand how a pin and tumbler system functions.

Inside every pin and tumbler lock is a cylinder (or key cylinder.) Within the cylinder is a chamber (the plug) containing stacks of pins. The pins it contains vary in length. When the correct key is inserted into the cylinder, the ridges or teeth on the key match the pins inside. Rotating the key causes the pins to spring apart and the plug to rotate. This rotation releases the latch from the door jamb.

Trying to insert the wrong key will produce one of two results. Either the key will not enter the cylinder at all, or, it will enter the cylinder, but won’t be able to rotate the plug because the match is incorrect.

Old-school lock picking usually requires a broad range of tools. Lock bumping, in contrast, requires only one special key. A lock bump key looks like an ordinary door key. It would be unlikely to draw any suspicion, were it to be used to gain illegal entry to a home.

To the untrained eye, a bump key might pass for a regular key. A closer inspection, though, would reveal that the teeth (or ridges) and the notches are even. All of the cuts, in fact, are made to maximum depth. They may also be referred to as “dummy keys” or “999” keys. The number “999” is derived from the fact that the cuts are all made to a depth of nine.

Opening a door lock with a 999 key isn’t as simple as simply inserting and turning. It does take a particular feel and a certain degree of practice, just as old-fashioned lock picking does.

What is alarming about lock bumping is that only two tools are required: a 999 key and a small “bump tool.” A would-be criminal will draw much less attention to himself with a bump key than with a set of locksmithing tools.

Two other major factors increase the likelihood that home and business or commercial property owners will become the target of a lock bumper:

1) Lock bumping can be learned from the Internet. Unfortunately, the World Wide Web is rife with how-to video teaching this practice.

2) Bump keys can be purchased relatively easily over the Internet. It’s almost as easy as finding how-to videos.