Abstract: A fastener comprising a fastener body and a fastener head is disclosed. The fastener body has a threaded portion and defines a longitudinal axis. The fastener head is arranged at one end of the fastener body, and comprises a tool engaging portion. The tool engaging portion comprises a plurality of alternating lobes and flutes forming a multilobular surface pattern, each lobe having a driven surface arranged to engage with a driving surface of a tool, and a trailing surface arranged opposite to the driven surface. The driven surface and the trailing surface extend substantially parallel to the longitudinal axis defined by the fastener body. The trailing surface of at least one lobe is provided with a modified zone in which a diameter of the lobe is increased, said modified zone providing a wedging effect between the tool engaging portion and a tool. In the fastener of the invention wobble between the fastener and a tool is significantly reduced.

Abstract: A screw (1, 2) includes two recesses (5, 6) in the side of the shank, said recesses being arranged diametrically opposite one another, where each recess is shaped as two plane segments extending substantially parallel to the axis of the screw and along a portion of the shank length.