Abstract: The invention relates to a system for securing a cover on a container by providing a retaining mechanism having a projection that is received by corresponding apertures and/pr cavities in the cover and container, thus preventing the rotation of the cover with respect to the container. The cover can include a projection, such as a gas outlet, by which the retaining mechanism can be anchored to the cover. A sealing assembly can be received in the gas outlet, and include a projection extending outward from the gas outlet thus preventing the removal of the retaining member until the sealing assembly is removed. Preferably, the sealing assembly also closes a gas aperture in the cover when inserted into the gas outlet.