Openings around boxes in noncombustible surfaces must not exceed ¼ inch to prevent fire spread. Boxes must be securely fastened to the structure using approved methods such as: Boxes must remain rigid and protected from physical damage. A distribution box is a key part of electrical systems in buildings. Inside, you'll find parts like circuit breakers and fuses that protect the system from problems like overloads and short circuits. The box usually contains switches, fuses, or. For procurement professionals, electrical contractors, and project managers, choosing the right Distribution Box (DB Box) is a critical decision that directly impacts system safety, reliability, and long-term operating costs.