Mounting Method: The box should have appropriate mounting holes or brackets for secure attachment to the surface. I need an electric box to do the splice / connection of the light fixture. The diameter of the hole is about 3 5/8", and its depth is about 1 1/2". The closest thing at my big box store was a 3-1/2" x 1/2" pancake metal. When installing 4 square boxes inside a wall to be covered, you need to use a box with a bracket. Installation is quick, clean, and non-invasive, making it perfect for concrete walls, rental spaces, or temporary setups. What Is A Surface Mount Box? A. Yes, surface mounted sockets are safe—and convenient.