When a player knocks in the game of Gin Rummy it means that he has reduced his hand to the maximum points allowed by what the value of the knock card is. This means for example if the knock card was a seven, then the person who is knocking has seven or less points left in their hand. Remember if the knock card is an Ace then it must be played to Gin.
A player can knock in any turn of play, but it must be after drawing and before discarding his final card. If he forgets to knock before he discards then he cannot do so until the next play of his hand which happens after his opponent has his chance to play. When the player knocks, he must clearly state his intention. He can do this in four different ways. They include:
• Saying the word “Knock”
• Announcing the total numerical value of his unmatched hands, also known as the count
• Exposing his entire hand arranged into matched sets and unmatched cards
• Discarding face down next to his hand, never on the discard pile. If the player places the card he is discarding on the discard pile then it is considered to be cheating and the hand will have to be forfeited.
After knocking the count is figured by placing value on the unmatched cards. The melded cards are counted as zero and placed into piles separate from the unmatched cards. The unmatched cards are then given points based on the value of the card. For example, if you have a 2 and a 3 that are unmatched, then your count is 5. If you have a 2, 2, and a 3 then your count is 7, and so on. A ten, jack, queen, or king is valued at 10. An ace is valued at one.
After the player has announced his count, the opponent must then expose their hand to all the players in the game. The opponent is permitted to reduce his hand by placing any melds that he has on the table separate from each other. He can then take any unmatched cards from his hand that meld with the player’s hand that knocked and reduce those to zero, also called laying off his cards. For example if the player that knocked had a meld of ace, two, and three of hearts and the player that did not knock had the four and five of hearts, he is permitted to lay off those two cards to the knockers cards. This will essentially reduce his count, and may possibly reduce it enough to underknock his opponent which will be explained later. The player that knocked is not allowed to lay off any of his unmatched cards to his opponents, and if your opponent called gin you are not allowed to lay off any cards even if you have cards that can be laid off.