A tied hand is not that common in gin rummy, but when it does happen you need to know how and why you proceed the way you do. On occasion, the play of the hand proceeds to the point where one of the players draws the 50th card of the deck from the stock. If this happens it of course only leaves two unused cards in the deck or stock. The player who draws the 50th card may knock or go gin at that point. If the player does not go gin or knock then the player must discard and his opponent has the right to pick up the discard and use it.
That player may use the card to create a meld, or to add to an existing meld so that he further reduces his hand value. However, he cannot take the card and simultaneously discard it in order to knock the hand the he was previously able to knock. In other words, if he already has a hand he can knock he can’t pick up the discard and place it right back down to knock or go gin. He must discard a different card completely.
If neither player knocks or gins then the deal is over. The hand has been played “to the wall” as it is called in a tied hand. It is essentially considered a draw and neither player is awarded any points. The same dealer that dealt that hand will re-deal and you will start the play over with the same knock card.
If you are wondering why you only draw to 50 cards instead of 52 you are not alone. The reason for this goes way back to almost the conception of the game. Some players when dealing carelessly will allow their opponent a glimpse of the bottom card in the deck. This lets the opponent know what the card is and that it will remain out of play for most, if not all of the game. This gives the opponent a very large advantage, especially if it is a card that he needs to make a meld. It may only be one card, but that card can make a huge difference in how the hand is played by the person who saw the bottom card.
If the play went down to the last card the person who knew the card could essentially control the play of the hand to bring it down to the last card. That means they could control the picks from the deck so that he would be sure to obtain the bottom card. Obviously this is cheating, but many people have done it, and if given the opportunity, many more would. This advantage would be so great that it would more or less overcome any other opportunities that the opponent might have. With the last two cards being completely left out of play then there is no advantage to either player and it just makes the play that much more interesting.