The Pin tumbler lock is the most widespread lock in the western world. Pin-tumbler locks have been around in some form since 2000 BCE. The Egyptian form of this lock was large, heavy, and made of wood, with pins made of metal, usually bronze, but sometimes iron. This design in its modern form was first patented in 1805 in England. The patent holder was an American named A.O. Stansbury. In the middle of the 18th century, the American locksmiths Linus Yale Sr. and his son, Linus Yale Jr., refined the lock design into the form recognizable today. These early versions of the pin-tumbler lock were expensive to produce, and did not become widely available until mass production became feasible.