Until 2004, Kryptonite locks used the tubular pin tumbler locking mechanism. A common example of a linear cam is a key for a pin tumbler lock. It was based on earlier Egyptian locks and Joseph Bramah's tubular pin tumbler lock. The pin tumbler is commonly used in cylinder locks. One of the animated displays shows how a pin tumbler lock works. For a time, many U-locks used a tubular pin tumbler lock. A tubular pin tumbler lock is a pin-tumbler lock with a round keyway. Pin tumbler locks are still the most common kind of mortise lock used today. A pin tumbler lock is composed of a series of spring-loaded stacks called "pin stacks".