In gin rummy, there is an old adage that many people still play by. It is “When in doubt – knock!” In the early play of any hand except if you can go gin, you should knock the first chance you get, when it is the safest to do so. As the hand progresses to the middle and late stages, there are also times that are important for you to knock.
One of those reasons is if all of your matched sets are dead or practically dead. That means that if all or most of the cards you need have already been discarded or are being used in sets that your opponent holds. You should knock, even if you are sure you are going to lose the hand. If you don’t knock, your opponent is sure to go gin and the resultant loss will be greater than if you make a sacrifice knock. The only reason you wouldn’t do this if the resulting knock will cost you the game by the score.
In knocking for any reason, you should always meld your hand in a manner that will afford your opponent the least number of lay-offs, even at a cost in points to you. If you are playing a hand strictly for a knock, at this point in the late game, sets of the same value are more advantageous than sequences, since they allow less lay-off possibilities. When you have a choice of how to lay a meld, you should keep in mind the lay-off possibilities and those cards that your opponent already has in runs and cannot be layed-off on your hand.
Similarly, it may sometimes be wise to discard from a run when you are knocking. This can prevent lay-offs that could cost you dearly. There may be times when your opponent has nine melded cards and is holding up the one card that can be layed-off with your hand. In that case, breaking up the run will cause him to have to hold onto that card, eliminating the underknock.
When playing for a knock, you should always remember that a three-card combination has four possible ways of being filled. If possible, you should try to add a fourth card to such a combination, thus giving you eight options. It is wise to do this even at the expense of throwing a fourth card off a four-card meld.
Another tip to remember is that a combination of four cards that total no more than the allowable knock value is as important a factor in your hand as a meld. It should not be broken up to increase one’s meld opportunities or defensive plays any more than a meld would. Even if two of these cards can be combined by taking an opponent’s discard, allowing you to knock with a lower number of points, it will not change the number of melds that you will have to pick.