To me, it looks like a symbol you would use to denote electricity present. I'd say it was meant to say that an electrical box or some other piece of infrastruct

To me, it looks like a symbol you would use to denote electricity present. I'd say it was meant to say that an electrical box or some other piece of infrastructure had electricity present. It could even be a non-standard symbol for a ground. edit: the right angle portion of it looks like the symbol for 3 wire 2 phase electricity used here - https://www.conceptdraw.com/How-To-Guide/qualifying-symbols https://www.conceptdraw.com/How-To-Guide/qualifying-symbols ..Yes, it is just a right angle. but I could see the electricity symbol being overlaid to indicate that it was an electrical symbol.