A fastener (2) such as a rivet, and a method of manufacture of such, wherein the fastener (2) is formed with helical (16) and annular grooves on the shell (4), such that when the fastener (2) is installed into a workpiece (24), a bulb (30) having a lobed blindside footprint (36) is produced on the blindside of the workpiece (24), the helical grooves (16) having an increasing depth towards the head end (12) of the shell (4) to promote formation of the bulb (30) initially towards the head end (12).