Typists do it with their fingers. TV evangelists do more than lay people. UNIX don't do it. Undertakers do it with corpses. Unix wizards do it with unchecked conversions.
Ushers do it in the dark.
Ventriloquists do it with ther mouths closed. Veterinarians are pussy lovers. Violinists do it with long strokes. Volleyball players keep it up. I GIs did it over there.