Lock Bumping - Open locks with a bump key

Lock bumping is a technique used to open locks using a filed down key that is the same profile as the lock. This means that the key needs to slide into the lock but doesn't have to turn. The way to make a "bump key" is to file down the notches to the same height, as shown in the picture below.

Once the key is filed down you slide it into the lock and apply a small amount of pressure using your thumb pushing the key to the left or right depending on which way the lock turns to open it. You then tap it with something popping the lock and the key will turn. It's not easy to explain so I've found a video with a demonstration on how to do this.

Here is a video showing you how it works using a cross section animation. This might make it easier to understand.