A junction box is an enclosure that contains the wiring intersections that connect the house's internal wiring to the main power supply provided by the local utility company. Junction boxes are square or rectangular in shape, and they usually feature either a hard plastic or metal material.
Plastic is a nonconductive material, so plastic boxes don't require a ground wire, and they are inexpensive and easy to install. They come with markings that help to correctly align the box. However, the nail brackets are also plastic, and they can render the box unmountable if they break. Metal boxes are more resistant and better suited for commercial, ceiling and external applications.
Junction boxes are installed outdoors or indoors, attached to a wall or recessed. They either come with a front door or a front panel that opens upward or downward, granting access to the wiring. Junction boxes have the potential to last decades, but they need to be replaced when damage occurs or when additional wiring is necessary for the home.
Modern junction boxes come with a safety switch that shuts down the power in case of an emergency. Indoor recessed are easy to hide by using a painting or other type of wall decoration. Junction boxes conceal and protect the wiring of a home, minimizing damage when the system overloads and produces sparks.