Which of the following is a requirement for screws penetrating the box walls in a junction box?

The requirement for screws penetrating the box walls in a junction box to have blunt ends is rooted in safety concerns. Blunt-ended screws minimize the risk of injury during installation and subsequent maintenance work. By ensuring screws do not have sharp points, potential injuries to individuals working near the junction box can be reduced. This is particularly important in environments where wires may be exposed and accidental contact could occur.

In addition to safety, the use of blunt-end screws helps to prevent damage to the internal wiring and components within the junction box. Sharp ends could potentially pierce insulation, leading to short circuits or other electrical hazards. Therefore, the blunt ends of screws serve the dual purpose of enhancing safety and protecting the wiring system.

The other options do not align with the NEC requirement for safe installation practices associated with junction boxes.