To be able to use proper judgment in ridding yourself of cards
that you fear may block your partner’s suit, you should thoroughly
understand the leads, and above all things, you should have perfect
confidence that your partner has made the correct one. Remember that
a high card led against a “no-trump” declaration indicates great
strength or great length, and that you can rarely lose more than one
trick by throwing your own high card on the one led by your partner;
whereas a failure to unblock will often occasion the loss of several
cards in your partner’s hand. If you hold four cards in the suit that
your partner leads (provided of course the lead is high) save the
lowest card, playing the third best to the first trick, and then play
up. With five cards, play the fourth best to your partner’s high card
lead, and then play up or down as the situation demands.
With length in the suit that your partner leads, especially as an
original opening, it is often advisable to indicate your strength
by playing first a high and then a lower card. This echo or signal
encourages your partner to continue the suit.
With three cards in your partner’s suit two of which are honours, the
lower of the honours should be played to the first trick. By playing
the lowest card of all you will invariably block the suit.
With three cards including but one honour, the middle card should be
played to a high card lead, and the honour should be thrown or played
to the second lead. Be careful to return the highest card of your
partner’s suit, as this will minimise loss from blocking and allow
your partner to continue the suit without interruption.
The following are given as examples of unblocking:
+-------------+----------------+----------+
| HOLDING | ON PARTNER’S | PLAY |
| | LEAD OF | |
+-------------+----------------+----------+
| J 9 8 7 2 | K | 7 |
| J 8 5 3 | K | 5 |
| K Q 7 | A | Q |
| Q J 8 | K | J |
| K Q 5 | J | Q |
| Q 8 3 | K and A | Q on A |
+-------------+----------------+----------+