An inclinometer or clinometer is an instrument for measuring angles of slope (or tilt) of an object with respect to gravity. It is also known as a tilt meter, tilt indicator, slope alert, slope gauge, gradient meter, gradiometer, level gauge, level meter, declinometer, and pitch & roll indicator. In the case of a ship, the clinometer showed the roll of the ship in in the waves, with an allowance of a 50 to 70-degree tilt to either side before possible capsizing. Clinometers came in a variety of styles, but most simply a pendulum would point to a halfmoon ruler, with the centered 0 being upright and anything above 0 being a roll in either direction, up to the maximum measurement of the clinometer.