To use, run the wire through the hole at the end of the tool. Then, with the wire on the round side of the tool, attach the end of the wire in the hole midway up the tool, locking it in place with the set screw. Move the tool on the inside of the vehicle, a few inches at a time, while the person on the outside follows doing the cutting. The smooth metal will move under the moldings and along the dash and prevent damage