the game is generally played by two players, each receiving ten cards
a standard deck of 52 cards is used.
the cards have values as follows:
the first dealer is chosen randomly by drawing cards from the shuffled pack - the player who draws the lower card deals. subsequently, the dealer is the loser of the previous hand (but see variations). in a serious game, both players should shuffle, the non-dealer shuffling last, and the dealer must then cut
each player is dealt ten cards, one at a time
the twenty-first card is turned face up to start the discard pile and the remainder of the deck is placed face down beside it to form the stock
the object of the game is to collect a hand where most or all of the cards can be combined into sets and runs and the point value of the remaining unmatched cards is low
a card can belong to only one combination at a time - you cannot use the same card as part of both a set of equal cards and a sequence of consecutive cards at the same time. for example if you have 7♣7♠7♥8♥9♥ you can use the 7♥ either to make a set of three sevens or a heart sequence, but not both at once. to form a set AND a sequence you would need a sixth card - either a 7 or a 10
in Gin Rummy the Ace is always low. ♣A23 is a valid sequence but ♣AKQ is not
a normal turn consists of two parts:
you must begin by taking one card from either the top of the stock pile or the top card on the discard pile, and adding it to your hand
the discard pile is face up, so you can see in advance what you are getting
the stock is face down, so if you choose to draw from the stock you do not see the card until after you have committed yourself to take it. if you draw from the stock, you add the card to your hand without showing it to the other players
to complete your turn, one card must be discarded from your hand and placed on top of the discard pile face up. if you took the top card from the discard pile, you must discard a different card - taking the top discard and putting the same card back in the same turn is not permitted. it is however legal to discard a card that you took from the discard pile in an earlier turn or took from the stock just now
for the first turn of the hand, the draw is done in a special way
first, the person who did not deal chooses whether to take the turned up-card
if the non-dealer declines it, the dealer may take the card
if both players refuse the turned-up card, the non-dealer draws the top card from the stock pile
whichever player took a card completes their turn by discarding and then it is the other player’s turn to play
you can end the play at your turn if, after drawing a card, you can form sufficient of your cards into valid combinations: sets and runs. this is done by discarding one card face down on the discard pile and exposing your whole hand, arranging it into sets (groups of equal cards) and runs (sequences)
any remaining cards from your hand which are not part of a valid combination are called unmatched cards or deadwood. and the total value of your deadwood must be 10 points or less
ending the play in this way is known as knocking, because it used to be signalled by the player knocking on the table, though nowadays it is usual just to discard face down
knocking with no unmatched cards at all is called going gin, and earns a special bonus
a player who can meet the requirement of not more than 10 deadwood can knock on any turn, including the first
a player is never forced to knock if able to, but may choose instead to carry on playing, to try to get a better score
the opponent of the player who knocked must spread his/her cards face-up, arranging them into sets and runs where possible
provided that the knocker did not go gin, the opponent is also allowed to lay off any unmatched cards by using them to extend the sets and runs laid down by the knocker - by adding a fourth card of the same rank to a group of three, or further consecutive cards of the same suit to either end of a sequence
cards cannot be laid off on deadwood. for example if the knocker has a pair of Twos as deadwood and the opponent has a third Two, this cannot be laid off on the Twos to make a set
if a player goes gin, the opponent is not allowed to lay off any cards
the knocker is never allowed to lay off cards on the opponent’s sets or runs
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
some play that after the player who took the third last stock card discards, the other player can take this discard for the purpose of going gin or knocking after discarding a different card, but if the other player does neither of these the hand is cancelled
each player counts the total value of their unmatched cards. if the knocker’s count is lower, the knocker scores the difference between the two counts
if the knocker did not go gin, and the counts are equal, or the knocker’s count is greater than that of the opponent, the knocker has been undercut - in this case the knocker’s opponent scores the difference between the counts plus a 10 point bonus
a player who goes gin scores a bonus 20 points, plus the opponent’s count in unmatched cards, if any
a player who goes gin can never be undercut - even if the other player has no unmatched cards at all, the person who going gin gets the 20 point bonus and the other player scores nothing
the game continues with further deals until one player’s cumulative score reaches 100 points or more
when the game is over, the player with the lower score pays the player with the higher score an amount proportional to the difference between their scores
some play such that the winner of each hand deals the next. some play that the turn to deal alternates
some people play that
some play that the bonus for an undercut, the bonus for going gin, and the box (bonus for each game won) are all 25 points
some play that if the loser failed to score during the whole game, the winner’s entire score is doubled