Five-suit bridge called "Castle Bridge", in which the fifth suit of Castles looked like a Rook chess piece and was colored green. This pack reused the diamond courts for the new suit. The manual that came with this deck did not use Marseille's rules but Ammiel F. Decker's 1933 rules. Ultimately, the complexity of adding a new suit to the game led to it falling out of popularity by the summer of 1938. The rules are similar to regular contract bridge but the new fifth suit is ranked higher than spades but lower than no-trump in bidding. Decks usually came with one
Vanderbilt Club summary, Vanderbilt Club is: Vanderbilt distinguishes between informatory doubles and business doubles, two expressions known from auction bridge. Doubles should be informatory at the one-level; at the two-level if neither you nor your partner has previously bid; and perhaps at the three-level, depending on the player's judgment of the score and the bidding. Doubles should be made more freely in contract than in auction bridge, because the potential profit is greater. Vanderbilt does not otherwise discuss bidding in contested auctions. Vanderbilt describes three types of invitations to slam: bidding more than is needed to score game; bidding the opponents' suit;