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There are round, square, rectangular, shallow, weatherproof, and extension boxes. Electrical boxes come in plastic and metal varieties. Plastic boxes are non-conductive and are relatively inexpensive. They come in different styles that either nail on or are the cut-in variety.

Metal cable and conduit depend on the contact from its metal sheathing to the metal box to complete grounding. Even if the device does not complete the ground, Romex or NM wiring can always be used with metal electrical boxes by attaching the bare or green grounding wire to the box by a screw.

In general, it recommends plastic boxes for switches and receptacles and metal boxes for light fixtures. Metal boxes are required when the existing wiring in the home is metal clad cable and must be bonded to the ground wire.

Electrical wires are typically exposed in the attic, crawl space, or at the electrical panel. Look for the word "aluminum" or its element symbol "AL" on the plastic wire jacket. If the market isn't visible, trace the wire until you find an area where the metal is exposed and not hidden by the insulated jacket. AL wire often mimics the metallic grey

The front edge of the box must be flush with the finished wall surface, usually 1/2-inch-thick drywall. You can use a scrap of drywall to position the box.