Abstract: A lockable closure plug consisting of a top-flanged cylindrical resilient compressible body with a top plate covering the top of the body and a flat bottom plate engaging the bottom of the body, and an axial operating stem rotatably engaging centrally through the body and abutting on the top plate and threadedly engaged through a nut secured centrally to the bottom plate. A rod-like handle bar is secured perpendicularly through the top end of the stem and a pair of link bars are pivoted to opposite sides of an upstanding U-shaped bracket on the top plate. The link bars in raised positions can lockingly receive the handle bar therebetween, and said link bars are apertured to receive the hasp of a padlock, which can hold the link bars in raised locking positions.