When branch-circuit wiring is fished in existing hollow spaces, device boxes must be secured to what?

When branch-circuit wiring is fished in existing hollow spaces, the device boxes must be secured to the finished surface. This practice ensures that the boxes are properly aligned and accessible for device installation and maintenance after the walls are finished. By anchoring device boxes to the finished surface, it provides stability and support for the outlets or switches that may be installed within those boxes, promoting safety and functionality.

Securing device boxes in this way also helps to avoid potential conflicts with building integrity, as it ensures that the loads they carry are adequately distributed and supported by the surrounding materials. Properly secured boxes minimize the risk of movement or dislodgement over time, which could lead to wiring hazards or electrical failures.

Although securing to stud framing, ceiling joists, or floorboards are structural methods that might seem beneficial, they do not specifically address the requirement of having the device boxes easily accessible and securely fixed within the context of finished spaces. Thus, securing to the finished surface is the preferred and correct approach in this scenario.