Today’s tip is about why you lead fourth highest when you make the opening lead in a long suit.

The main reason to lead fourth highest is to give partner an idea of how many cards you have in the suit.

• With four cards in your suit, your fourth highest lead will be your lowest card.
  Example: You decide to lead a spade from ♠Q1052. Lead ♠2.

• With five cards in the suit, your fourth highest lead will be your second lowest card.
  Example: You decide to lead a spade from ♠Q10852. Lead ♠5.

When you have led fourth highest, your partner can then judge how many cards the declarer has in the suit and whether your partnership has a greater combined length in the suit than your opponents.

Your partner needs to look to see if you have led your lowest card or your second lowest card. If your partner can see that there is no lower card missing after the lead, then partner will know you have four cards in the suit.

Example: North declares 3NT and east leads ♠3. The dummy south reveals ♠J52 and west has ♠A86. When west plays ♠A, north plays ♠4. West can see that there is no missing card lower than east’s ♠3 so west knows east has led from a four-card suit.

If partner recognises that there is a lower spot card not visible after the first trick, then partner should assume the player who made the opening lead is likely to have that card and so will have led from a five-card suit.

The trick is to look under the card led to see if there is a lower card missing.

Example: North declares 3NT and east leads ♠5. The dummy south reveals ♠J72 and west has ♠A94. When west plays ♠A, north plays ♠6. West can see that ♠3 has not been played to the first trick. East is likely to have ♠3, so has led from a five-card suit.

Why is this important?

If you know how many cards your partnership has in the suit led, you can judge whether your side is likely to make a length trick in the suit. Your partnership usually needs seven or more cards to make a length trick.

If the lead to a notrump contract reveals that your opponents have greater length in the suit than your partnership (your partnership has six or fewer cards in the suit led), then it is not likely you can establish a length trick in that suit.

You should switch to a suit where your partnership is likely to have seven or more cards.

Example: North declares 3NT and east leads ♠3. The dummy reveals ♠J52 and west has ♠A6. West plays ♠A which wins the trick. Should west return a spade or switch to a different suit?

West knows east has just four cards in spades as east has led their lowest card. As west has only two cards in spades, west knows that the partnership has only six cards together. West should switch suits.

In trump contracts you can also use the same knowledge about partner’s length in the suit led to decide how many rounds of the suit can be played before the declarer trumps.

Example: North declares 4♥ and east leads ♠3. The dummy south reveals ♠KJ64 and west has ♠AQ82. After south plays ♠J, west wins ♠Q and the declarer plays ♠9. Should west now play ♠A?

No! Assume east has led ♠3 from a four-card suit. West has four cards in spades, east has four cards, the dummy has four cards, so this leaves north with just one card. If west plays ♠A, north will trump and can then later win south’s ♠K.