Lower the notches on each end of the cable tray over the brackets, and slide the tray (either toward the front or back of the desk) until they click into place. Run the power cord through the cable tray. See. This publication is intended as a practical guide for the proper and safe* installation of cable ladder systems, cable tray systems, channel support systems and associated supports. Cable trays are essential for supporting our electrical and data cables in modern buildings. But getting them installed. Wall supports RVK are used for mounting 40 mm height KR-type cable trays to wall, mounting rails AS, ceiling supports HK1, HK2 and TP2 from the inner side of the cable trays.