Abstract: A closure assembly comprises a closure body adapted to be disposed in an opening in a structure. A closure body has a spirally disposed groove provided therein. A retaining member is made to be flexible for movement within the groove. Apparatus is operably connected to the closure body for moving the retaining member through the groove to a position wherein a portion of the retaining member engages the structure. The retaining member is further made of a size and material having sufficient shear strength to prevent movement of the closure body when the pressure applied thereto generates a force against said retaining member.