Metal boxes are grounded and bonded to maintain electrical continuity and ensure safety. Fasteners entering the wiring compartment must not damage conductors or compromise insulation. Improper screws can create safety hazards. What is the difference between thermoset and thermoplastic materials? You can find distribution boxes made from various distribution box materials such as steel, aluminum, PVC, polycarbonate, high-density polyethylene, and thermoset plastics like SMC. Each distribution box material has its own. ility in mind. A conduit body is a removable-cover section of a conduit system that provides access at junctions or termination points.