A Weld nut is a special type of nut specifically designed to be welded to another object. The common weld nuts are hex weld nuts and square weld Nuts.The vast majority of weld nuts are manufactured in low carbon steel or stainless steel. This is due to the methods currently available to spot weld or projection weld the hardware to joining material. Aftermarket products such as zinc plating are sometimes used to coat low carbon weld nuts giving it the rust resistant properties of stainless steel at a substantial cost saving.