Funny story . . . some years ago, I drained the oil in my lawn mower at the end of the season, squirted some in the cylinder, but didn't refill the crankcase.
So I wouldn't forget the crankcase was empty in the spring when I needed to resume lawn mowing, I taped a sheet of paper to the top of the mower with the (I thought) clear message - NO OIL.
My mother visited and happened to see it from the other side, and asked "What does 710 ON mean?"
It's now a standing joke in my family . . .