With a "Crescent Wrench", it's not just push/pull, but how you load the movable jaw...the weak point of the design. You want to load the jaw as close as possible to it's root. You can see this easily by loosening the wrench so's it's a loose fit on a large-ish nut or bolt head. Try it, mark the point of the hex with a Sharpie, then flip it over and pull again, and mark again.
Mike Haverly and I were talking about this once. When I worked for Boeing, we had a shop edict that we would have to take our "Crescent Wrenches" home, because they were tired of their toolpost nuts and such being battered and rounded off. I talked to my Leadman and told him that I really hated Crescent wrenches, and didn't use it, but would feel nekkid without it. He said "Ok, fine, keep it." He also let me keep a lead hammer, tho we really weren't supposed to have them. Ok on most materials, but death on Titanium. Mike said that when he went to work at Boeing, they had a test to take, and one of the questions was which way to pull on a Crescent Wrench. They said he was wrong, to which he disagreed and proved his point. Turned out that an Engineer had written the test!
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Certainly NOT Howard or Paul.
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Steve