Weld backup tools Strong magnetic base Electric weld will not stick to the copper pads For use with TIG and MIG electronic welders Keeps wire from going through holeThis tool saves time and labor by providing quicker, cleaner welds. The copper pad dissipates heat. Position magnetic base so that the copper pad is behind joint or hole to be welded. Adjust knob up or down so that copper pad is flush against the back of void to be welded, and weld up hole. Remove tool and grind the excess weld.