This is a nice tool for loosening stubborn screws when you don't want to strip out the driver slot. Twist the head for clockwise or counter-clockwise rotation. Set the driver bit in the screw slot, and smack it straight on with a two pound hammer. Inertia of the hammer impact holds the driver bit in the screw head as internal cam action applies extraordinary high torque to the scew. It works well for door hinges and striker plates, brake drum screws, or any slotted screw that wants to be stuck tight. The tool has a standard 1/2 inch square drive (sometimes 3/8 inch) so you can use standard wrench sockets on it. This picture shows a 1/2 inch drive tool with a 3/8 inch drive adapter (lower left).