Patent ID: 8747044

Claim:
A fastener, comprising: a threaded shank having a central longitudinal axis and defining a pitch diameter extending through the central longitudinal axis; exactly three lugs extending from and positioned on an end of the threaded shank at approximately 0, 120 and 240 degrees around the central longitudinal axis of the threaded shank, wherein each of the lugs comprises: structural ribs; and a radially-outward end portion comprising: a tightening surface; and a loosening surface; wherein the tightening surface and loosening surface are angularly offset from each other and meet at a corner; and wherein the tightening and loosening surfaces are adapted to be driven by a rotation of a hex head tool in a tightening rotational direction and a loosening rotational direction, respectively; and three concave surfaces, wherein each concave surface extends between adjacent pairs of the three lugs, respectively, and wherein the concave surfaces do not extend closer to the central longitudinal axis than the pitch diameter.