Abstract: A golf green level determining removable accessory for temporary securement to a shaft of a golf putter, to in effect create a level tool having the length of the golf putter. With this accessory temporarily in place, the golfer lays his or her putter at selected places on the contour of the grass surface of a golf green to determine the respective slope in the selected locale. A housing of this accessory positions and holds an elongated sealed liquid and air level; receives and holds at least one magnet; temporarily receives, via a concave portion thereof, a portion of the shaft of a golf putter; receives some calibration shims or an adjustable set screw, to initially, when necessary, adjust the level air bubble at the zero position, when the golf putter is laid on a known level underlying surface with the accessory in the temporary position thereof. If a golf putter has a nonmetallic shaft, then a metal snap on partial sleeve is placed on this shaft.