From Hatsumi's Rokushaku Boujutsu DVD from Quest: "There is for instance this Kukishin-ryu staff which has nine iron rings attached. Thus, it will stop when you slide it through your hands. So for a head strike, one may hold it here (grasps hold of bo between the inner most ring and the next), or stop the hand here and strike (moves hand along bo one more ring). Or stop at the last ring and strike (self-explanatory). This way you gradually move inside toward the opponent." the rings are there as a way of measuring distance.