The tank's rivets were also apparently flawed, and cracks first formed at the rivet holes. About of rivets came from the Clyde Rivet Company of Glasgow. A rivet is a permanent mechanical fastener. A single eyelet reinforces the spoke hole much like a hollow rivet. Trigger guard now wider and attached with Rivet and one screw. The wheels were steel bowl/aluminium rim rivet compound wheels. A friction-lock rivet cannot replace a solid shank rivet, size for size. By 1928, the George Tucker Eyelet company produced a "cup" rivet based on the design. In 1951, A325 bolts were recognized as equivalent to a hot driven ASTM A141 rivet. The piston strikes against the rivet set. Rivet diameters and lengths are measured in millimeters. The stress and shear in a rivet is analyzed like a bolted joint. The bucking bar deforms the tail of the rivet. The first were specialty clothing store chains called Copper Rivet, Sagebrush, and Tansy. This product was later developed in aluminium and trademarked as the "POP" rivet.