Rivet

A small pin-type fastener, used to fasten pieces of sheet metal together. Most aircraft rivets are made of aluminum alloy and are driven cold. The rivet is slipped through holes in the material being fastened, and a heavy steel bucking bar is held against the end of the shank. The head of the rivet is hammered with a rivet gun (an air hammer). The bucked head, or shop head, that is formed when the rivet is driven, is flat on top, and its sides are rounded.