The goal
In Gin Rummy you sort your ten cards into sets and runs. Whatever is left over is deadwood. Get your deadwood low enough to knock, and end the hand before your opponent does.
The deal
Two players get ten cards each. The next card is turned up to start the discard pile and the rest is the stock. Aces are low and count one. Face cards count ten.
The up-card is offered to the non-dealer first, then the dealer. Taking it counts as your draw, so you discard next. If both pass, the non-dealer starts with an ordinary draw and may still take it.
The play
Draw one card, from the stock or from the top of the discard pile. Then discard one. You may not throw back the card you just took from the pile, the up-card included ("You cannot put that straight back."). That is the whole turn.
A set is three or four of the same rank. A run is three or more in sequence in one suit, with the ace only at the bottom. You never declare your melds. The best arrangement of your hand is worked out for you.
When your deadwood is ten or less you may knock as you discard. That ends the hand. The knock rides your discard, so it is judged on the ten cards left. A table set to Gin only allows no knock short of gin. There is no big gin: even with all eleven cards melded you still discard, and it scores as an ordinary gin.
When a discard without a knock leaves two cards in the stock, the hand is dead. Nobody scores, the hands are not shown, and the same dealer deals again. You may still knock on that last discard, and then the hand counts as usual.
Knock when you safely can. Waiting for gin is worth 25 more, but every turn you wait is a turn your opponent may knock first. A knock near ten is thin: your opponent only has to match it after laying off. Knock lower when their pile takes fit your melds. A pile take tells your opponent what you want. Late in the stock, a safe discard, one they cannot use, matters more than a lucky draw.
Scoring
On an ordinary knock your opponent's loose cards are laid off onto your melds for them, sets and runs alike, in whatever way cuts their deadwood most. Then you score the difference between the two deadwood counts. Your melds are always the arrangement that leaves you the least deadwood, so you cannot hold one back to block a lay-off.
Knock with no deadwood at all and that is gin. You score their whole deadwood plus twenty-five. They may not lay off anything, and a gin can never be undercut.
If their deadwood ends up equal to or lower than yours, they have undercut you. They score the difference plus twenty-five. A tie goes to the defender, so a knock at exactly ten is a real risk.
Winning
Hands are played until somebody reaches the target, one hundred unless the table picks 150, 200 or 250. There is no game, box or shutout bonus: your total is the sum of your hands. The deal changes after every scored hand. After 60 hands the leader wins, and an exact tie there has no winner.
