A boomerang is an example of gyroscopic precession. The popular variety at left is thrown by grasping it at the bottom and throwing it so that it rotates about an axis perpendicular to the plane shown. This plane is tilted enough from the vertical enough to get enough lift to keep the boomerang airborne. The cross-section at each end is shaped as an airfoil with its leading edge pointed so that it is facing forward when that end is at the top. The airfoil causes it to "fly" in the direction thrown, but the higher aerodynamic lift on the top end creates a torque which causes the angular momentum to precess, gradually changing the heading of the airfoil and moving it in the curved path.