Burn-through is a common welding defect, especially on light gauge materials, that results in holes instead of sound welds. It is often confused with melt-through, which can be acceptable, but true burn-through weakens joints and leads to scrapped parts. The main causes include excessive amperage, poor fit-up, and operator error, all of which make penetration harder to control. Solutions range from adjusting amperage and travel speed to improving upstream processes like cutting and forming, and investing in welder training. By understanding and addressing the root causes, fabricators can dramatically reduce rework, improve weld appearance, and lower overall costs.