Used to support the 6x4 and 4x4 systems attaching to any 3/8 inch (9.5mm) x 1 1/2 inch (38.1mm) or 3/8 inch (9.5mm) x 2 inch (50.8mm) ladder rack rail. Adjustable to nine incremental positions from 4 inch (101mm) to 12 inch (305mm) above or below the ladder rack. No threaded rod required. The pre-assembled slide clamps enable fast assembly to channel. Use 7/16 inch nut driver on slide clamps.