"The lever tumbler lock... could still be picked. It merely required more skill and time."
Jock Dempsey, blacksmith
People depend on their locks and keys a lot more than they would like to admit. Without having to stand guard over their possessions from morning to night, they are free to pursue their lives away from their homes and businesses. Locks and keys existed before Robert Barren patented his tumbler lock in 1778, but the sheer number of people now carrying keys to tumbler locks testifies to the success of his invention.
Barren's lock, which offered considerably improved security over any previous locks, was called a double- acting tumbler and was very similar to many modern models. A tumbler, essentially a lever inside the lock, prevents the bolt of the lock from being opened unless it is raised to a certain height. Barren's lock employed two tumblers and these needed to be lifted to different heights for the bolt to be released.
Most focused thieves could still pick the Barron lock if they had enough time, so in 1818 Jeremiah Chubb added a detecting feature in hopes of winning a reward of £100 offered by England's Portsmouth Dockyard. The detector consisted of either a spring or a specialized lever that would catch any tumbler that was raised too high. If an unlucky picker raised any tumbler higher than the detection point, the lock would jam shut, vanquishing the thief. The jammed lock would also alert the lock's owner, who could reset the lock simply by using the original key.
