We've all been there: you pull on the wrench with all your might but the nut or bolt won't budge. So you soak the thing with penetrating oil, heat it with a torch, and try again – this time with a cheater bar on the wrench. Still no go. Time to get serious.
So you put someone else's wrench on the bolt and beat on it with a hammer (hey, you're not going to do that to your own wrench – are you?) while screaming your choicest bolt-loosening words. Maybe it works. Maybe it doesn't.
Two things, though, we can be certain of: The folks working nearby will have gotten an earful and someone (you or the guy whose tool you borrowed) now has a beat up or broken wrench.
Enter the striking wrench. It's designed to be beat on with a hammer or sledge. It wants you to beat on it. And when you do, that stuck nut or bolt will beg for mercy.
A number of companies (such as Stanley Proto, JH Williams, Wright Tool, and Gearench) make striking wrenches. I saw these wrenches from Martin Tools at last year's STAFDA show. The largest one here fits 3 3/4-inch fasteners, but their stock models go up to 4 3/4 inches.
I can't help wondering how big a sledge and how hard a swing it would take to loosen a frozen 4 3/4-inch nut. I'd be willing to try but would have to learn some new bolt-loosening words (mine only go up to 1 1/8-inch).