Well Snap On calls them spiral sockets. I know Sears Craftsman makes a set also. Basically they are a socket with sharp reverse flutes inside. You find the appropriate size and tap it over the rounded head of the bolt with a hammer. Using a ratchet (perferably with a long handle for torque) slowly try to take it off. The socket has reverse flutes so as you try to back the bolt out the flutes dig deeper into the metal. They work great and every tool box should have a set. To be honest I have three sets and use them extensively. Now you can break them if you're really torquing down, but if you get impact rated they rarely do. I have a set of Craftsman along with the Snap-on and they all work well - besides if you break it you can take it back to Sears as they warranty their tools.