Abstract: A cap is disclosed for closing an aperture having a camming surface extending axially inwardly about its periphery. The cap includes a first body portion having a diameter larger than the aperture and a second body portion having an outer diameter smaller than the aperture. A gasket is disposed adjacent the first body portion. A first slot extends diametrally through the second body portion. Second and third chordal slots extend partially through the second body portion and are parallel to the first diametral slot. The first, second, and third slots define first and second parallel lever arms. Each lever arm includes a portion extending radially beyond the outer diameter of the second body portion to engage the camming surface of the aperture.