I'm installing some lights in my basement, and will be replacing the single gang box in the hall (currently only for hall light) with a double gang box. The idea is to accommodate the hall light switch and the basement light switch in the same box, but I want to inform anybody who comes after that they will have to turn off two breakers to safely work in the box.
What's the best way to label the box, so people know there are two circuits in the box?