What is Lock Bumping?

Lock bumping is a method of opening a pin tumbler lock or a cylinder lock using a tool called a bump key or rapping key and slight pressure. In the 1970s, locksmiths in Denmark developed the earliest forms of bump keys which opened cylinder locks by using manual pressure. In the 21st century, home security experts brought lock bumping to light and began to talk publically about the method as a home security threat. So whether you're looking to hone your locksmithing techniques or want to learn new ways to protect your home, it's wise to learn about lock bumping.

How Lock Bumping Works

So how does lock bumping work? In a pin tumbler lock, an outer casing has a cylindrical hole in which the plug is housed. Pin tumbler locks have a series of spring-loaded stacks (called "pin stacks") with two pins - a key pin and a driver pin - that are stacked on top of each other. To open the lock, the plug must rotate and the gaps between the key pins and the driver pins line up with the shear line. With pressure by the user, either with a single tap or a series of taps, the bump key pushes the pins up for a split second so that the plug can turn and the lock is opened.

Lock Bumping Tools

Professional locksmiths may use specific tools to bump locks, such as a bump hammer that makes striking the end of a bump key easier by applying the proper amount of energy to bounce the lock pins without losing control of the key. An over-the-key plug spinner tip helps locksmiths avoid bumping a lock in the wrong direction by fitting over the bow of just about any bump key without the need to insert another tip in the keyway.