cli.gs In this jam-packed book you will learn the following: ✔ Locks: A Crash Course. To understand how lock bumping works, to use bump keys, and defend against this easy entry method you NEED to know how pin tumbler locks work. ✔ Bumping Theory: We discuss the principles behind bumping using laymen terms so anyone can follow. If you’ve never bumped a lock before this is the chapter to start with. Some of the topics covered: the perfect angle of a homemade bump key, what makes a bump key ...