The weld nut you're referring to is known by various names, including "Flange Weld Nut - Projections Opposite Barrel Side" and "Round Base Projection T-nut." These T-nuts feature a round base or flange with three projections on the side opposite the barrel. These projections are used for resistance welding the fastener to the base material. Electric current is directed through these projections to generate sufficient heat, melting both the projections and a portion of the base material. Achieving a good and reliable weld requires the correct combination of current, pressure, and time. One of the advantages of projection welding is its ability to reduce marring of the base material's surface, providing a clean and effective fastening solution.