Definition: Junction boxes are metal or plastic, measure 2 1/2 inches or 3 1/2 inches deep and it's where wires go to live when they are joined together. Boxes that measure 2 x 3 and 2 1/2 inches deep generally contain 3 wires. Boxes that measure 2 x 3 and 3 1/2 inches deep are made for five wires.
Secure a junction box to a strong structural member such as a stud or joist if the box will be used to support a light fixture. Other types of junction boxes have wings that fit inside a cut-out drywall hole, but they will not support a light fixture.
Use a cable clamp to secure ROMEX wiring that comes into the box, and cap wires inside the box with wire nuts. If you have difficulty twisting the wires together, use a needle-nose pliers to twist black to black and white to white.
