the pin 46 being of larger diameter than the recess 68 of the sealant end 70 causes the end of the sealant plug 34 receiving the pin to expand radially if there is no such recess 68 the pin makes its own recess as the insertion process proceeds in either instance it radially expands the portion of the expandable sealant plug 34 into which the pin extends this expansion assures a tighter gripping relation between the sealant plug on the one hand and the retainer legs and the retainer ring on the other hand the expandable sealant plug 34 has some spring like resiliency somewhat like a dry foam rubber which provides resistance to laterally inward movements of the retaining leg snap hooks which is overcome by the camming action of the aperture perimeter or rim on the camming surfaces 54 of the retaining legs during insertion of the subassembly 32 into the body member cavity 30 this spring like resiliency resistance aids in preventing the snap hooks from becoming unhooked from the aperture perimeter or rim once the snap hooks have hooked under it after the shaped expandable sealant plug 34 is formed and the plug has been inserted into the retaining legs 44 of the retainer cap 40 the subassembly 32 so formed by the plug and the cap may be temporarily.