Abstract: A golf ball being adapted to be capable of being stroked in the direction in which the center of gravity of the ball is made to coincide with the center thereof. Marks are placed on the ball to identify hit points and lead points, the hit points being those at which a first diameter line passing through the center of gravity of the ball intersects the surface of the ball and the lead points being those at which a second diameter line perpendicular to the first diameter line intersects the surface of the ball. Alternatively, marks capable of identifying the direction of the diameter line joining the hit points are set on the lead points.

Abstract: A ladder wherein a plurality of rounds are pivotally and turnably mounted to and between the right stanchion and the left stanchion at proper spaces, and supporting arm levers are detachably fixed from both stanchions to the round by bolts or machine screws.