Square weld nuts are fasteners designed for welding onto metal surfaces, offering strong, permanent attachment points. The square shape provides stability during welding, and weld projections ensure a secure bond. Plain finish means they are uncoated, suitable for environments where corrosion resistance isn't critical. DIN 928 is the standard defining their size and quality. These nuts are commonly used in industries like automotive and metal fabrication where components need to be securely fastened from one side.