When building the wall, the reserved hole shall be about 20mm larger than the length and width of the distribution box. 1)The distribution box shall be installed in a concealed way. Whether you are installing outlets, switches, lighting fixtures, or junction connections, box size directly affects wire fill capacity, device fit, and installation quality. Check for proper IP/NEMA ratings and material quality. Practice good wiring: secure. This guide explores control panels, electrical boxes, breaker panels, bus bars, junction boxes, and custom enclosures to help you understand their sizes, types, and common applications. Used in industrial automation and process control.