"Vestil plain trolley has been designed to quickly install on virtually any S-type I-beam. Width is adjusted by rotating the center rod with lifting eye clockwise or counterclockwise Once hoist sold separately is attached, center rod cannot be rotated which prevents trolley width from accidentally changing Lifting eye is located at the bottom of the trolley for attaching a hoist sold separately Painted finish Push-type operation 2 1/2in. to 8 5/8in. I-beam flange 3in. headroom"