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Socket holders allow the bulb to be secured into place, and also enable switching bulbs when needed. They typically come in plastic, ceramic, or metal, depending on the type of bulb they support. Switches are used to open and close electrical circuits when turning lights on and off. Switches can be single, referred to as single-pole, or multiple-way. Individual switches are helpful, as they allow workers to turn off unnecessary lamps that are not in current use resulting in lower electrical costs.