How did Robert Barron’s double-acting tumbler lock improve lock security?

Robert Barron’s 1778 patent for the double-acting tumbler lock represented the first significant advancement in modern lock security.1

Prior to this innovation, locks were more easily bypassed. Barron’s Barron lock improved security by utilizing two tumblers—levers or pawls that fall into a slot in the bolt to prevent movement. To successfully operate the lock, the key was required to lift each of these two tumblers to a specific, different height to clear the slot before the bolt could be moved.1

By requiring multiple tumblers to be set precisely, Barron introduced a design principle that remains the foundation for all modern lever locks.1