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). Cable trays are a support system for electrical cables, power, signal, and communication and optical fiber cables. NEC Article 392 governs cable tray installations, covering tray types, fill. NEC Article 392 explains cable trays, their components, appropriate wiring methods for cable trays, and instances where they are and are not permitted for use. It also focuses on construction and installation practices for cable trays.