US Patent 7240378 Flange valve

A flange valve to deter entry of rodents and pests, insertable on existing devices, comprising a unidirectional swinging door attached on an inner wall of a frame, the door and the inner wall of the frame having a clearance between them of a dimension not allowing entry of rodents and pests. The design of the frame is catered to the desire of the user and may be a laterally protruding ring having a central circular opening and openings along the edges for the insertion of bolts or screws; a laterally protruding ring on one peripheral edge of an open cylindrical body; a cap having a flat top with a central circular opening and openings for the insertion of bolts and screws; a conduit; or a wax free toilet bowl gasket, a toilet flange or a wax ring used in the installation of toilet bowls.