The Casino's stopped using it a long time ago , but basically a player drawing 5 cards without hitting 21 was an automatic winner (or in some variations at least guaranteed not to lose) The reason it's no longer used is that it would favor the player - it reduces the house edge by 1.46% Automatic Winner Charlie Rule in ...

If the dealer's hand exceeds 21, all players with 21 or less win. If your hand is higher than the dealer's, without exceeding 21, you win. If you have the same total as the dealer, it's a push even if you got blackjack. A Blackjack will beat 21.