Warning phrase

What is the most often warning phrase in print?

I'd guess "Close cover before striking." Why?

'Not to be taken internally'(?)

DFG

Slippery when wet. (?)

© Copyright.

Wet Paint (a little flexible with 'in print', but still.)

DFG

I was originally going to go with "close cover before striking," but when I saw it taken, I had to go to Plan B. As long as we accept it as a (legal) warning, I think © copyright is right on the money. It's in every book, newspaper, magazine, pamphlet, brochure, catalog, package, label, tag, you name it, that has been published for the last century plus.