When ordered with the rack, the troughs ship assembled, but not installed. When ordered separately, the trough will still ship assembled. The top of the DCE rack has a variety of mounting holes. Place the trough where you require cable routing. Insert a cage nut into the appropriate square hole on the top panel, and secure the trough on top with M6 screws. For 600mm wide racks use DCE6016, for 700mm wide racks use DCE7016 and for 800mm wide racks use DCE8016.