Knocking in Gin Rummy

The knock rule

On your turn you draw a card, giving you eleven, and then discard one. If the ten cards you keep can be arranged so that the unmatched cards, the deadwood, total 10 points or less, you may knock as you discard. The hand ends immediately.

• Melds are sets of three or four cards of the same rank, or runs of three or more consecutive cards in one suit. A card can belong to only one meld.
• Deadwood is everything not in a meld. K♠ Q♠ 4♦ unmatched is 24 points; 4♦ 3♣ 2♥ unmatched is 9.
• Knocking is optional. You may keep playing with low deadwood in the hope of going gin.
• You cannot knock by discarding the card you just took from the discard pile. That card must stay in your hand for the turn; knock by discarding another card, or wait.
• 0 deadwood is gin, not a knock. It scores more and shuts out the lay-off.

If the stock runs down to two cards without anyone knocking, the hand is a draw and nobody scores.

Laying off

After a knock, the knocker lays down their melds and deadwood. The defender then lays down their own melds and may lay off: any of their deadwood cards that extend one of the knocker's melds are added to it and stop counting against them. A 7♣ goes onto the knocker's 4♣ 5♣ 6♣; a fourth King goes onto three Kings.

Lay-offs only go one way. The knocker cannot lay off on the defender's melds, and the defender cannot lay off at all after a gin. On CardCouch the lay-off is worked out automatically when a hand ends, and the hand-end panel shows which cards were laid off, so you can see exactly how the deadwood totals were reached.

This is why a low knock is safer than a knock at exactly 10: the more deadwood you leave the defender room to shed, the more likely they finish at or below your count.

Scoring a knock, and the undercut

Once lay-offs are done, compare deadwood. If the knocker's count is lower, the knocker scores the difference. Knock with 6 against 19 and you score 13. There is no bonus for a plain knock.

If the defender's count is equal to or lower than the knocker's, the defender has undercut the knocker. The defender scores the difference plus 25, and the knocker gets nothing. Knock with 9, and if the defender lays off down to 9 the defender scores 0 + 25 = 25; down to 4 and they score 5 + 25 = 30.

Gin is a knock with zero deadwood. The defender may not lay off, and the knocker scores all of the defender's deadwood plus 25. At the end of the game the winner also collects a 100-point line bonus and each player 25 per hand won, which the scoring guide explains in full.

When to knock and when to wait

The rule most good players follow: knock as soon as you can, early in the hand. In the first five or six turns your opponent is usually carrying 30 to 50 points of deadwood, so a knock at 8 or 9 scores 25 to 40 and there is little for them to lay off. Waiting for gin risks two things: they knock first, or they meld up and turn your late knock into an undercut.

Knock now when

• It is early and your opponent has taken few or no cards from the discard pile.
• Your deadwood is 5 or less; there is little room for an undercut.
• The stock is getting low. A drawn hand scores nothing, so any legal knock beats none.
• You are close to 100 and the knock finishes the game.

Wait when

• You are one card from gin with several outs, plenty of stock left, and your opponent has shown little. The 25-point bonus plus their full deadwood is often 40 or more.
• Your opponent has picked up three or more discards and is probably close to knocking themselves, so your 10-point knock would likely be undercut. Either lower your deadwood first or switch to safe discards.
• Your deadwood is exactly 10 and made of cards that fit your opponent's likely melds (they get laid off, but yours do not).

The computer opponent on CardCouch follows the same logic: it knocks when it can, but plays on for gin when it is very close and the stock is deep.

Knocking on CardCouch

After you draw, tap or click a card to select it. CardCouch arranges your best melds for you and shows the deadwood you would hold after discarding that card. Try a couple of candidates; the number updates each time. When it reads 10 or less the Knock button lights up next to Discard, and at 0 a Gin button appears too. The status line also tells you "knock available" or "gin available" the moment your eleven cards allow it, so you never miss the chance.

When the hand ends, both hands are shown with melds, deadwood and any lay-offs, and the score sheet records whether it was a knock, gin or undercut. Games run to 100 points.

Worked example