In DOT-speak, that stands for Center High-Mounted Stop Light, ie the 3rd brake light. Has anyone added one to the back of their camper? As far as I know there are no laws requiring one, but the safe...
I've seen new cab/chassis trucks with a new custom haulers bed/feed bed/work bed types with LED stop/turn at the normal location at the bottom/rear of the bed and another set at the top at each corner of the headache rack. Damz things were too bright.