Proto Clik-Stop

A nice little 6-inch adjustable wrench from my shop.  Interesting that the forging includes both "Canada" and "U.S.A." suggesting that wrench blanks were first made in the States and then sent to Canada for finishing.

The "clik" aspect was patented in 1959, with the patent assigned to the Pendleton Tool Company, which later renamed itself Proto. Basically, the inventor put teeth on the bottom of the worm which, under the compression of a spring, engaged with similar teeth on the recess in the wrench, such that the movable jaw was locked in place when applied to a fastener, and less likely to back off if the worm was accidentally touched.  It was called a "clik-stop" because you could hear the teeth click as they engaged.  (Sadly, mine is too worn to make this sound anymore.)

The mechanism is still used on some Proto (now Stanley-Proto) wrenches today.  Not bad mileage from a 50+ year-old patent.