Copper Pad backs up hole, dissipates heat, and keeps wire feed from going through hole. Back side of hole welded is flat and does not require grinding, unless it is a finished surface. Holes can be welded faster at a low heat. Saves time. Cleaner welds, less panel distortion and flat weld inside panel This tool is designed to aide and speed up the welding of holes in steel body panels and general hole welding. The tool has a copper alloy pad that is placed behind the hole to be filled, and a magnetic base to keep it where it is placed. The arm and thumbscrew allow the tool to be used on radiused or uneven surfaces. For Tig and Mig welding, U.S. and International patents pending. Lifetime warranty.