Gin-Rummy Tournament Rules - details.

The standard Gin-Rummy rules claim, that play ends when a player knocks. This can be done on any turn (including the first), immediately after drawing, provided that the value of the unmatched cards in player's hand (after he discards) does not exceed 10 points (or less in Oklahoma Gin).

The common Gin-Rummy rules state, that the play also ends if the stock pile is reduced to two cards, and the player who took the third last card discards without knocking. In this case the hand is cancelled, there is no score, and the same dealer deals again.

The modern Tournament Gin-Rummy rules add some details to the situation when the stock pile is reduced to two cards. It is called the 50th card rule (the fiftieth card rule). If neither player knocks or gins and the 50th card is drawn from the stock pile, leaving two cards there, the gin-rummy tournament rule says, that the both players may have action on the 50th card. It means, that if one player draws the 50th card and doesn't want to knock, this player has to discard any open card to the discard pile. The opponent player has the option now to take this open card and knock or pass (do not take this open card) - in the last case the hand will be cancelled as described above.