The carpet spike(stinger) is an attachment that lets you power stretch without the poles. I used one years ago in mobile homes where the walls are too weak for a power stretcher. They are really not a good idea. Improperly used, they can put a large hole in the subfloor and can rip the carpet. They also will not get as good a stetch as using the tubes. And they can void the carpet warranty. I am sure that some installers using them have never had a problem, but it would only take once to get expensive.