Infomation: Klaverjas or Klaverjassen is the Dutch name for a four player trick-taking card game using the piquet deck of playing cards. It is closely related to the card game klaberjass, which is popular internationally and also known as Bela, and various other names. Enjoy playing this game.
Rotterdam rules: A player who cannot follow suit must trump if possible. A player who plays a trump must head the trick if possible, even if the player's partner currently heads the trick.

Amsterdam rules: Undertrumping is only allowed when it cannot be avoided. A player who cannot follow suit and whose partner is not heading the trick must head the trick if possible.
Aces and tens are high, i.e. cards in ordinary suits rank Ace, 10, King, Queen, Jack, 9, 8, 7. The Jack ("Jas") and nine ("Nel") in the trump suit, however, are the highest trumps. Thus trumps rank Jack, 9, Ace, 10, King, Queen, 8, 7.