If the knocker's count is lower, the knocker scores the difference between A player who goes gin scores a bonus 20 points, plus the. Gin Rummy is very similar to regular Rummy, but Gin has some additional wrinkles that make it a more interesting and challenging game. To play Gin Rummy. According to Hoyle's Rules of Games, Gin Rummy was invented in the early s by Elwood T. Baker of New York. Here are the complete. Wrong Card Discarded - If a player discards the wrong card when knocking, he may not retrieve it. If the upcard is a spade, the hand will count double. Not Helpful 2 Helpful 2. Some play that if the loser failed to score during the whole game, grand slem winner's entire score is doubled rather than just doubling the game bonus to After a player has gin, points are added, with cards on the table being added up and cards in hand being subtracted.