Muiderberg is a bidding convention in the card game
bridge. It is a two-level preemptive opening based on a two-suiter with precisely a five-card
major and a
minor suit (four-card or longer). In Muiderberg the 2
♥ opening denotes five hearts and an unknown minor suit, whilst 2
♠ denotes five spades and an unknown minor suit. The convention is also known as the Dutch Two, Lucas Two or Woo Two (mainly UK) opening.
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