A deck of cards is shown blank on both sides and the magician talks about how cards are printed - not by printing presses, but by magic. At the magicians command, a card appears - but it only has a face but no back! Then the magician "prints" a back but no face!
Finally the magician shows what a deck looks like that a magician has completely printed by making all the cards have both faces and backs! But a magician can always control the printing on the cards and with the snap of a finger they all turn blank again! Miraculous!