Abstract: A closure plug particularly useful in the manufacture of insulated closures such as refrigerator and freezer cabinets. The plug comprises a molded, one-piece resilient plastic body member including a peripheral portion for sealingly engaging the edges of an opening in the closure, a central portion extending inwardly from the peripheral portion and defining an aperture communicating with the opening, first and second relatively flexible flaps extending above the central portion and overhanging the aperture and first and second relatively rigid tabs extending from the central portion between the flaps toward the center of the aperture. The flaps are deformable past the tabs through the aperture of permit the insertion of an insulative foam introducing conduit into the closure. Upon withdrawal of the conduit, the flaps tend to return to their original position outside the aperture but are restrained from passing back through the aperture by the tabs.