Upper incoming line, lower outgoing line, main circuit on the left, control circuit on the right, horizontal and vertical. The concealed laying is mostly through the pipe and hidden in the building wall or. In this guide, we'll break down everything you need to know to install a distribution box correctly and confidently. Choose the right box based on environment (indoor/outdoor), load capacity, and durability. Check for proper IP/NEMA ratings and material quality. Ensure safe placement: install in. In modern electrical systems, cable distribution boxes (also known as electrical distribution boxes or distribution boxes) play a crucial role as the key hub for managing, distributing, and protecting circuits.