Public bathrooms that don't have paper towels invariably have electronic hand-dryers that blow hot air.  It's a painfully inefficient process, but hey, anything to save the environment.  Despite their fool-proof design and operation, instructions are necessarily, and they usually go something like this: 

1. Push button.
2. Rub hands under warm air.

I've been in public bathrooms all around the country and in all kinds of venues.  I don't think I've ever seen hand-dryer instructions that didn't have some variation of the following graffito (singular of graffiti ... c'mon, keep up): 

1. Push button.
2. Rub hands under warm hair.

I've seen this in schools, workplaces, public attractions, everywhere.  Either this specific graffito is so obvious that it practically writes itself, or there's a nationwide band of hoodlums systematically vandalizing public bathroom hand-dryers.  You decide.