Slip your double sided card into the deck. For this example, let's pretend that your double sided card has an ace of spades on one side and a three of clubs on the other. Spread the cards face up on the table in front of the spectator to show him that they are all different.
Remove the double sided card with the ace of spades showing face up. Tell your spectator that you are going to make the ace disappear, but that you need to enlist the help of three other cards. Take any three cards and place them face down in a pile next to the ace.
Tell your spectator that you are going to put the ace on the bottom of the pile. Slide the ace into the pile but, instead of putting it on the bottom, place it second from bottom. This takes a little practice, but if you do it quickly and confidently, your deception will not be noticed.
Perform an Elmsley count. An Elmsley count is a card sleight in which four cards appear to be counted by the magician, but in fact only three cards are shown, as the top card is counted twice. If you do not know how to perform an Elmsley count please see the reference section of this article. If performed correctly, the double sided card will now be on the bottom of the pile.
Allow the double sided card to fall naturally in your palm. With your free hand, straighten the remaining cards. Doing this will momentarily shield the double sided card from view. Quickly turn over the double sided card so it now shows the three of clubs. At this point, quickly spread the four cards out face up on the table. The ace will appear to have vanished.