Slang name is a porkchop, comes from the shape. Some semis use an inner and outer nut to secure the duals. Outer holds the the outer tire on. When you go to remove the outer sometimes it spins the inner nut loose at the same time. When that happens, hopefully it was just on one stud, you remove the rest of the nuts and that one as the last one. Switch to the square drive socket and slip that tool over the outer nut and that little foot at the end drop into the lugnut hole next to the one you are working on. Step on it with your foot and tighten the inner lugnut untill it drops out of the outer.
It has become an old school tool as most trucks now have gone to a unimount style or also called hub piloted wheel. It only uses 10 lugnuts per wheel position instead of the 20 that a regular budd wheel used. Also the left side wheels were left hand thread. Budd inner capnuts are famous for breaking off and being a large pain to remove