A common joint found in auto repair work, the lap joint is a piece where two pieces of metal overlap each other. An ideal lap weld should have a good amount of weld bead penetration without the upper edge melting back or overlaying. If the upper layer melts too much, the lap joint will be too weak and thin. Making lap welds takes a good amount of practice to get it right, so experiment with your welding angle, arc length and rate of stitching welder travel to find the best combination for you.