The decision of when to knock, play for gin, or play for the underknock often depends on the condition of the score and on your hand.
If you are on a schneid, then you should knock as quickly as possible. Though you may have a very good hand, you need to remember that your opponent may hold an equally good one. This is especially true if you are behind in points, and you are in the later stages of the game. At this point, he can afford to play for the gin bonuses, but you can’t. Do not take the chance of going for gin now. You need to score first, and then resume the normal risks of playing for gin in the next hand. When the situation is reversed and you have your opponent on a schneid, you have the luxury of playing for a quick knock or going for gin, depending on the condition of your hand.
While getting off a schneid or keeping an opponent on a schneid are the most dominant situations in any game, most hands should be played to win the maximum number of points. Sometimes you can win more points with a weak knock then you can with a good gin. In such a case, you should play to knock as quickly as you can, instead of waiting for gin.
There are other hands which should be played for the sole purpose of underknocking your opponent. In addition to the bonus boxes, the underknock has another benefit. If accomplished two or three times in the same set, your opponent will be so badly upset psychologically that he will be afraid to knock again. This will prevent him from winning hands that he ordinarily would have won.
Knock, under most conditions, is the most valuable word in the game of gin rummy. It should be utilized at the first opportunity, with a few exceptions. They are:
• When the knock is an Ace and the hand becomes a must-gin situation.
• When the odds are in favor of your going out in a game, or obtaining enough score to catch up to your opponent.
• When it is a reasonable assumption on your part that you stand to be underknocked by laying off his cards.
• When you know that your opponent is not in a position to knock his hand
• When you have your opponent’s hand dead.
• When your hand has the characteristics of a gin hand.
Knowing when to knock, play for gin, or underknock is an essential part of any hand, but no more so than the later stages of the game. That is when you get to a point that you are either going to win big or lose bigger, and you have to know when to keep going and possibly end up losing, or get it over with. Each player will handle each hand differently but if you want to become an expert you have to learn the basics of each in the later stages of the game.