What is an undercut in Gin Rummy?

The undercut is Gin Rummy's built-in punishment for a careless knock. It turns a hand you thought you had won into a loss, and it is why knocking is always a calculated risk.

Quick answer: An undercut happens when the knocker's opponent finishes with equal or less deadwood than the player who knocked. Instead of the knocker scoring, the defender wins the hand and takes a 25-point undercut bonus plus the difference in deadwood. It is the penalty for knocking too greedily against a strong opposing hand.

How an undercut occurs

After a player knocks, the opponent reveals their melds and lays off cards onto the knocker's melds to reduce their own deadwood. If their remaining deadwood is equal to or lower than the knocker's, they have undercut the knocker.

The undercut bonus

The undercutting player scores a 25-point bonus plus the difference between the two deadwood counts. So a knock that goes wrong does not just fail to score, it hands a sizeable bonus to your opponent. Only a knocker with genuinely low deadwood is safe.

Avoiding the undercut

You cannot be undercut if you go Gin, since the opponent cannot lay off against a Gin hand. Otherwise, the defence against undercuts is to knock only with very low deadwood and to read whether your opponent is close to melding, as our when to knock answer explains.

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Related questions

What does it mean to knock in Gin Rummy?

Knocking is how you end a hand of Gin Rummy without going Gin. Once your unmatched deadwood totals 10 points or less, you can knock: place your final discard face down, lay out your melds, and reveal your deadwood. Your opponent then lays off cards, and the player with the lower deadwood total scores the difference.

How do you lay off cards in Rummy?

Laying off means adding a card to a meld that is already on the table, rather than starting a new one. In Gin Rummy, the defender lays off deadwood onto the knocker's melds to lower their own count. In games like Rummy 500 and basic Rummy, you can lay off onto any melds in play to unload cards and score.

When should you knock in Gin Rummy?

Knock when your deadwood is low - ideally well under 10 - and the risk of an undercut is small, especially early in a hand before your opponent has built their melds. Hold out for Gin when you're one card away and confident, or when your opponent looks close to going out and a slim knock could be undercut.