Our Device allows for quick and easy installation by homeowners. The Device simply drops into the floor drain until the SENTINEL drain cover is resting on the floor. Secure the SENTINEL in place by fully tightening the TWO screws which will splay expandable rubber side seals against the adjacent drain pipe wall while simultaneously anchoring the Device into place. This creates a redundant watertight seal between the pipe and the Device. In an inactive position the ball float rests at the bottom of the Device allowing for normal use water drainage to occur. If a backflow of sewage were to occur, the ball will float up to engage with a primary and a secondary reformable rubber gasket that will envelop the top surface of the ball creating a water tight seal.