Abstract: A cover for openings in a partially assembled missile or aircraft structure to prevent entry of chips, oil or other debris during further machining or other manufacturing operations. The cover has a central elastically compressible plug section adapted to fit snugly in an opening and an outwardly extending flange around one end of the plug. When the plug portion is inserted into the opening, the flange covers a ring of bolt holes surrounding the opening. The plug is formed from an elastic closed cell foam material and preferably has a cross-section slightly larger than the opening so as to be compressed slightly when inserted in the opening. The cover is coated with an elastomeric polyurethane coating to prevent flaking of the foam plug when inserted and removed from the opening and to prevent adhesion of contaminates to the cover. Because of the compressibility of the plug, each cover can be used with similarly configured openings of slightly varying sizes.