You can buy a set of specialty sockets for square nuts from $nap-on, or another tool supplier. Check at your FLAPS, they might have them. I don't know that Sears has them these days. I don't have any, and generally use the following procedure. Penetrating oil, open end wrench, then grinder,sawzall, or gas-axe. Ahh the escalation of violence. Generally though, Brad is right, they just brake. I work on old wooden boats, and up into the sixties and even later, many of the fasteners are square nuts. Made up at the yards, or bought buy the keg. I'll tell you one thing, if you can find an old keg of the hot dipped galvanized fasteners, they will last virtually forever on your truck, and are much easier to remove than stainless steel if you brake one, and the threads don't gall like stainless on stainless. Of course, this is all coming from someone who not only likes the square nuts, but also likes old slot drive screws, and the Yankee Driver.
