Patent ID: 7597518

Claim:
A fastener apparatus for securing a workpiece, the fastener apparatus comprising: a frusto-hemispherical head having a top surface, a curved outer surface, a base, and a peripheral edge; a downwardly-appending lip extending from the head curved outer surface and defining an annular recess within the head body, the annular recess having a substantially flat upper surface and a substantially vertical sidewall transitioning from said substantially flat upper surface to the downwardly-appending lip, the lip having a curved outer edges a curved lower edge, an inner edge having a curved lower portion and the vertical sidewall terminating in the annular recess and defining an annular recess height; and a shank connected to the head base and bearing screw threads and a tip; and an annular gasket, the annular recess and the annular gasket being sized such that when the fastener apparatus is fully secured to the workpiece, a first portion of the gasket protrudes from the frusto-hemispherical head to provide a first seal, a second portion of the gasket resides and is compressed between and surrounding the curved edge of the lip and the workpiece to provide a second seal and a third portion of the gasket remains within the annular recess to provide a third seal.