The device consists of a circular base – the bottom is flat and the top is a curved surface on which a small ball can roll. When the base is placed on a sloped surface, the ball rolls down due to gravity – this is resisted by the curved surface and friction. The bigger the slope, the further away from center is the final resting position of the ball. A transparent cover on the base protects the top surface of the base. This top surface will have markings to indicate the angle of the slope.