Originally Posted by
FBinNY
I used one many years ago. The nice feature isn't that it locks, but that the lever presses the worm gear in tightening the fit slightly. This ensures a super fit, and prevents rounding at high torque. Think of it as the love child of a vise-grip, and an adjustable wrench.
It's great for breaking tight nuts loose.
Yeah, it also lets you take it off the bolt/nut easily after you use it. With most adjustable wrenches if you get the movable jaw tight against the bolt so it won't slip, it's difficult to turn the worm to get it loose again.