This is the classic Three Card Monte but done with dominoes. Two double fives and one double one. You mix up the dominos. No matter how closely the spectator watches, he will never fine the double one. He will be completely fooled again and again.
"The Professor's Nightmare" is one of the most popular rope tricks of all time, and with good reason.
Here is an offbeat version that uses pictures of ropes printed on the cards. It packs very small, but plays very big.