A few years back, at the rural HS my wife attended way back when, maintenance personnel discover that there was evidence that someone had been crawling thru the AC duct work that connected the girls and boys locker rooms and showers.
The principal had them paint the inside of the ducts with some tar spray that would ‘mark’ the person crawling thru the system.
It didn’t take long.
The person they caught.....was a girl.............................
Hahahahaha. The little minx.