Gin rummy: strictly two players, melds stay hidden until the end, and you "knock" with 10 or fewer points of unmatched cards.; 500 rum: you score your own melds as you lay them, not just the opponents' leftovers.; Canasta: two decks plus jokers, partnerships, and seven-card melds.
Why people argue about this
In Gin Rummy, people often argue about whether a meld can be exposed before it's scored if they think it looks like a winner but forget that Section 6 clearly states melds stay hidden until the end. For Canasta, confusion arises because players sometimes misunderstand the "knock" rule; they believe you must knock with exactly 10 points of unmatched cards rather than any number under 10.
