Threaded shaft with Allen bit setting. Makes opening and closing the trolley to fit a beam ultra quick and convenient. Using a drill fitted with an Allen bit, simply work the trolley open and closed. Removes the need for collars/ spacers. This design provides best in class headroom and accommodates wider beam flanges. Comes with 8 Ft. Galvanized Hand Chain. Moves and hold trolley loads on a beam through the drive of a gear, controlled by the hand chain. Complies with ASME B30.11. Drop-protect side plates. Smooth travel. Minimum headrooM