A rivet's a permanent mechanical fastener. Before it's installed it consists of a smooth cylindrical shaft with a head on one end. The end opposite the head's called the buck-tail. On installation the rivet's placed in a pre-drilled hole. Then the tail's "upset" (for example deformed) so that it expands to about 1.5 times the original shaft diameter and holds the rivet in place. To distinguish between the two ends of the rivet, the original head's called the factory head and the deformed end's… (More on Rivets)