Play both ends against the middle
To play both ends against the middle is an American expression that dates from the late 19th century. It describes a strategy of duplicity whereby one favours both sides in an attempt to emerge on the winning side. It allegedly derives from the illicit practice of card dealers in faro, a card game which at one time was far more popular than poker in America during the 19th century. Faro was a bit like a game of roulette but instead of a numbered and coloured wheel, a complete suit of cards, traditionally spades, from ace to king was fixed to the table. Any number of players, as in roulette, would then place their bets on these cards. Pairs of cards, from a separate deck of 52 cards, would then be turned up, two at a time. The first card was called the banker’s card and any money placed on that value card, in the cards fixed to the table, would belong to the banker. The next card was the players’ card and the banker paid out even money to all players who had placed their bets on that card. Bets placed on cards that had neither lost nor won could remain where they were or could be moved to other cards if players so wished. There were other rules and different odds for bets placed in between cards, but essentially it was a simple, quick and easy form of gambling. Moreover, to obviate avoid sleight of hand in dealing cards, the banker would deal cards from a card shoe. Unscrupulous dealers, however, resorted to the practice of shaving small slivers off both ends of certain cards to ensure these cards were together after shuffling and then placed in the shoe. In faro, the banker won all bets when he drew an identical pair of cards. This practice was called ‘playing both sides against the middle’ and the source for this is explanation is Christine Amner The American Heritage Dictionary of Idioms.