Abstract: Apparatus for the fastening together of two or more sheets of material by means of an integral fastener consists of a longitudinally-movable pierce and extrusion punch, a cooperating longitudinally-movable pierce and curl die, and a segmented extrusion die surround the pierce and curl die. The pierce and extrusion punch and the pierce and curl die cooperate to pierce a hole through the sheets, and the punch and the segmented extrusion die then cooperate to push the material of one sheet through the other to form two coaxial tubes; thereafter the pierce and curl die curls the pushed-through material of the coaxial tubes back to effect the fastening, the apparatus providing a stationary anvil to cooperate with the pierce and curl die. The punch and the curl die are engaged by the ends of respective pivoted levers by which they are moved, and other ends of the levers being connected together; the ratio provided by the two levers differs so that the punch moves further and faster than the curl die.