A turn-and-bank indicator tells the pilot the attitude of the plane in the sky relative to the ground. This bank indicator uses a ball and curved glass tube to show rotation about the vertical axis. Gravity holds the ball to the lowest part of the tube, which moves from side to side as the airplane banks. The turn indicator uses a gyroscope to show rotation about the longitudinal axis. It has a pointer that indicates in degrees per unit of time the rate at which the craft is turning.