| 摘要 |
A device mountable within the thumb opening or thumb hole of a bowling ball which is manually adjustable to constrict the opening i.e., narrow the diameter of the opening of the thumb hole. A screw is threaded directly against a movable shoulder which narrows the opening for the thumb. Unscrewing or reversal of the screw causes the shoulder to move outwardly toward its orginal position to enlarge the opening for the thumb. The screw includes a bottom lip to prevent it from being totally unscrewed and the possible risk of loss. In a second embodiment, a screw serves as a cam rotator to move a cam on an eccentric toward the movable shoulder thereby forcing the shoulder to move inwardly and thus constrict the thumb opening. |
