A Horn or craps-11 bet, as it is typically called, is a one-roll wager that on the next roll of the dice their sum will be 2, 3, 11 or 12. If they total anything different (4, 5, 6, 7, 8, 9 or 10), you lose. If 3 or 11 appears, you are paid 15:1. If 2 or 12 rolls, the payoff is 30:1.
