B should pass both the queen and the knave. By passing the second trick, if the dealer fails to overtake, or if the dealer does not hold two re-entry cards, the suit cannot be made.
A♥ K♠ J♠ 9♠ 8♠ 7♠ 6♠ x-------x | Y | 2♠ | A B | A♠ 5♠ 4♠ | Z | x-------x [Q♠]
Y has an entry card. B should refuse to win the trick, trusting that Z has no other card to lead.
A♠ 10♠ 7♠ x-------x | Y | K♠ 6♠ 3♠ | A B | | Z | x-------x [Q♠]
A should refuse to cover the honour. If he waits until the third round, the suit is blocked. Z may have no re-entry card.
[Q♠] J♠ x-------x | Y | | A B | K♠ 6♠ 4♠ | Z | x-------x
In this case, the honour should be covered. If Z holds the ace, the suit is blocked.
A♠ J♠ 8♠ 6♠ 4♠ x-------x | Y | Q♠ 5♠ | A B | | Z | x-------x [10♠]
A should cover the ten led. It may establish the king and nine in B’s hands. If Y has no card of re-entry B can then hold up.
[K♠] x-------x | Y | | A B | A♠ 7♠ 5♠ | Z | x-------x
As Y has no other card to lead, B should refuse to part with the ace. Z cannot make the suit without two re-entry cards.
If you hold the commanding card of the adversary’s suit, endeavour to take out your opponent’s re-entry before the suit is cleared. It is equally important that you take out this re-entry card if you know that your partner has the command of the adversary’s suit. In extreme cases do not hesitate to sacrifice a king or queen in order to accomplish this purpose. When the dealer attempts to make a card of re-entry for an established suit, hold up a higher card in order to frustrate his scheme of play.
This part of the game merits much more consideration than a cursory knowledge of Bridge would suggest. The ordinary Bridge player is confused by the many difficulties attendant on discarding, and his cards are apt to be injudiciously thrown away. It would greatly simplify the discard if you were always to throw away your lowest card or to follow some other hard-and-fast rule; but, unfortunately, the discard is so affected by the particular situation and by the previous play as to preclude the possibility of establishing such a rule. When you advise the beginner to throw away a high card instead of a two spot, the situation appears to him hopeless; he fails to realise that at times high cards have little value, and, to obtain the lead, honours and even smaller cards must be properly protected.