Here we have just the tool for removing hex nuts which may be rusted solidly in place. It's a bit like a c-clamp on steroids with one sharp tooth. You clamp this on any stubborn hex hut, and tighten it with a wrench until it goes pop. The nut will split open and will be easily removeable without damaging the male thread. It works like a charm on nuts that are so badly rusted that you can't even find the corners. Do a web search to find the best price, cheaper than you might think. This one is K-D Tools model 715. See also J.C.Whitney.