Rummy in blackjack can refer to a popular form of blackjack side bet, commonly known as 21 + 3, or it could be a separate game where players combine their initial two-card hand with the dealers up-card to make Rummy hands. The Rummy side bet in blackjack works by combining the players initial two-card hand and the dealers up-card to make Rummy hands. A Rummy set is a three-card set that can be a 3 of a kind, a flush, or a straight. The Rummy side bet pays 9:1, and the house edge is 4.14% . Rummy blackjack is played at a table with space for 7 players and a dealer, much like traditional blackjack. Four to six decks of standard playing cards are used.