Page "Gin rummy" Paragraph 13

If all 10 or 11 cards in a player's hand fit into melds and thereby the player has no deadwood, he or she can choose to go Gin in which case the round ends and the player going Gin receives a Gin bonus of 25 points ( or another established amount ) plus any deadwood points in the opponent's hand.

The defending opponent can only lay out his or her melds and cannot lay off any deadwood into the melds of an opponent that has declared Gin.

A player can go Gin with a hand of three or fewer melds as long as all cards fit into a meld.