Fastener driving head

A fastener comprises an axially extending shaft (2) with at least a partial axially extending external thread (3) and having a leading end to be inserted first into a structure and an trailing end, a driving head (1) formed on the trailing end and extending transversely outwardly from said shaft (2), said driving head (1) having a first side (9) facing toward the leading end of said shaft and an oppositely facing second side, a plurality of webs (12) extending circumferentially around said first side (9) and having a trapezoidal cross section and extending in the axial direction of said shaft (2) outwardly from said first side (9), said webs having a first end at a circumferential peripheral edge of said first side (9) and a second end spaced radially inwardly from said first end and radially outwardly from said shaft with an annular space free of said webs between the second ends of said webs and said shaft (2), said webs having outside surfaces facing towards said leading end of said shaft (2) comprising a face surface (13) spaced axially outwardly from said first side (9) and a pair of spaced flank surfaces (14a, 14b) extending from said first side (9) to said face surface (13), and a radially extending space (b) between said flank surfaces (14a, 14b) of adjacent said webs (12) being constant for the full radial extent thereof.