The single loading dock traffic light set mounts to the wall on the outside of the dock to give a visual signal to truck drivers of when to stay in place at the dock, and when it is safe to pull away. Units do not come with a toggle switch for power or a flasher to make bulbs flash on and off. The polypropylene housing will not rust, pit, dent or corrode and is IP54 certified for indoor or outdoor use and come in either yellow or black. LED bulbs are used to reduce energy costs, require no maintenance and have a longer life span than incandescent bulbs.