How must surface extensions be secured over the box?

Surface extensions must be secured over the box mechanically to ensure they are stable and compliant with the National Electrical Code. Mechanical fastening provides a reliable method to secure the extension, preventing any movement or displacement that could compromise the integrity of the electrical installation. This adherence to proper fastening techniques is important for maintaining safety and functionality.

In the context of electrical installations, mechanical fastening can include using screws or other fasteners that provide a strong and lasting connection. This method also allows for inspection and maintenance, which is crucial for safety in any electrical system.

Other methods, such as gluing, taping, or leaving the extension loose, do not provide the necessary level of security and reliability required in electrical work. Gluing does not allow for easy access for future changes or inspections, while taping may not hold up over time, especially in environments subject to temperature fluctuations. A loose installation could lead to movement or disconnection, endangering the connected wiring and overall system. Thus, mechanical securing is the only acceptable approach according to code requirements.