Three players use the same scoring, the same board and the same 121 as two ACC r.1.2. What changes is the deal and the order.
The deal
The dealer deals 5 cards to each player and 1 card straight to the crib. Each player throws 1 card into the crib, so everyone keeps 4 and the crib holds four. The crib belongs to the dealer.
The play and the show
The player on the dealer’s left cuts the starter and leads. The play goes around to the left. When two players have said go, the third plays on alone, and the last card scores as usual. In the show, the player on the dealer’s left counts first, round the table, the dealer last, then the crib.
The deal passes to the left after each hand. These are the rules Pagat and most players use; the ACC writes its rules for two players.
Cribbage Street plays the two-player game.