[twobitshifter]

I’d wager the reason the the screw mechanism wasn’t designed to give a mechanical advantage is that it’s a part from a standard crescent wrench. The idea here was not to design a sliding lock mechanism, but to make a slide that can spin a regular crescent wrench.

Note that The crescent wrench already closes up linearly, so we’re just changing direction 90 degrees. There’s better ways to do that.