Abstract: A fastening system comprises a driving tool formed with a rectangular-shaped bit at its driving end, and a fastener such as a screw whose head is formed with a recess defining a central slot and four spaced undercuts each having parallel upper and lower walls and a side wall perpendicular thereto. The bit of the driving tool is inserted within the central slot of the recess and then rotated such that the side edges of the rectangular bit contact the side walls of two of the undercuts, and the top wall and bottom surface of the bit frictionally engages the upper and lower walls of such undercuts. Frictional engagement between the undercuts and the driving tool bit provides a positive, temporary interlock therebetween, and contact between the side edges of the driving tool and side walls of the undercuts permits the transfer of torque over a large surface to reduce wear.

Abstract: A screw driver has a handle, shaft and blade with the bottom edge of the blade being flat and having flat sides which incline inwardly from the bottom edge. To turn the screw, the screw driver is placed with its bottom edge in the gap between protruding (raised) quadrant sectors of the screw head and turned 45.degree.. The flat inwardly inclined sides of the screw driver act against cut-back flat sides of the protruding sectors to cam the screw driver toward the screw head and rotate the screw.