These hollow ended screw extractors will quickly & easily remove screws without damaging the surrounding area. To extract broken screws rotate the hollow extractor bit counter-clockwise slowly down over the screw, the bit should engage & unscrew it or the core around it. To avoid "dancing" guide it with a thru hole in ascrap piece of wood clamped in place (with the samehole size as the extractor in use).Size refers to thefinished hole size.