Patent ID: 8128667

Claim:
A closure for setting engagement with a structural member and comprising: (a) a substantially cylindrical body having an outer cylindrical surface relative to a central closure axis; (b) a substantially continuous guide and advancement flange extending helically about said outer cylindrical surface and being sized and shaped radially to interlock with a mating guide and advancement flange on a receiving structure; said closure flange having a leading surface and a trailing surface relative to a direction of forward advancement; said flange leading surface facing downwardly and generally sloping downwardly and inwardly toward said central closure axis; (c) at least one of said leading surface and said trailing surface being compound in contour and including a projection spaced from said body and extending outward in an axial direction from at least one leading surface or trailing surface and the projection having an inward facing anti-splay surface component facing generally toward said closure axis and being on the side of the projection closest to the body; the projection and anti-splay surface being sized and shaped to interferingly mate and radially interlock with reverse projections and anti-splay structure on a receiving structural member; (d) said body having a multi-surface aperture formed therein that is aligned with said closure axis and that is elongated along said closure axis, said aperture opening onto a trailing surface of said body and including a plurality of circumferentially spaced, centrally facing surfaces extending substantially parallel to said closure axis that are aligned to form a removal socket adapted to receive a removal tool; and (e) a break off installation head.