Can holes be drilled on the side of the cable tray

Due to their exposure to the open air because of the cable trays, the wires contained within need a very durable outer covering. The regulations dictate that the cables must either be Type TC (also known as Tray Rated) or must be metal-armored (Type MC). B-Line series KwikRail cable tray systems feature rungs with patented fastener holes, allowing installers to easily remove, reposition or add rungs. This is a description of how to select, install, and support these metal or plastic frames, on which electrical wires are installed. [pdf]