These trays are designed to protect wiring from harsh external conditions or where sparks, dust, or liquid contact must be avoided. Conceals cables for better aesthetics in visible. Cable trays, or carrier trays, are mechanical support systems for cables. They provide a robust structural that accommodates and safely transports cables from one point to another. Cable trays are normally classified by duty rating, which defines their load-bearing capability. Light. The cable trays do not build the wires in the thick pipes but rather leave them out in the open so that they can be seen and accessed. This article explains when to use each type based on the installation environment, cable thermal requirements, and applicable standards.