12 x 4 FiberRunner Brackets Used to support the 12x4 system from any new threaded rod extending down directly from the ceiling, grid, or ladder rack system. Two position height adjustments to accommodate system with or without hinged cover. Bracket is secured to threaded rod with two nuts. The pre-assembled slide clamps enable fast assembly to channel. Use 7/16in nut driver on slide clamps, For 16mm threaded rod.