Abstract: A threaded fastener which is constructed to be turned in one direction by a square socket drive includes a threaded stem and an integral modified head arranged with four raised projections which are circumferentially spaced. Each of the four raised projections includes a substantially flat wall portion and a curved and inclined ramp portion. The four flat wall portions effectively define a square center region which is compatibly sized to receive a one-half inch square socket drive. Rotation of the square socket drive in a counterclockwise direction causes the sides of the square socket drive to engage the flat wall portions so as to turn the threaded fastener in a counterclockwise direction. Any attempt to rotate the square socket drive in a clockwise direction causes the sides of the square socket drive to ride up along the ramp portions and ride out of engagement with the modified head of the threaded fastener.