The Rule of 11 is a mathematical corollary to fourth-best leads. It enables the third hand player to count how many cards declarer holds which are higher than the opening lead. The Rule works as follows:

- Subtract the opening lead spot card from 11.
- Also subtract the number of cards in dummy that are higher than the card led.
- Finally, subtract the number of cards in your hand that are higher than the card led.
- The final number equals how many higher cards declarer holds in the suit.

The Rule of 11 can be confusing, so it's easiest to demonstrate it with an example:

Partner | ||||

♠ 4 | ||||

Declarer | Dummy | |||

♠ ? | ♠ 10 9 6 | |||

You | ||||

♠ K J 5 |

Partner leads the ♠ 4. Assuming this is a fourth-best lead, how many spades are in declarer's hand which are higher?

- Partner's spot card is the 4, so 11 - 4 =
**7**. - Dummy contains three spades higher than the
♠ 4, so 7 - 3 =**4**. - You hold three spades higher than the
♠ 4, so 4 - 3 =**1**.

Thus, declarer holds exactly one card higher than the

Partner | ||||

♠ Q 8 7 4 | ||||

Declarer | Dummy | |||

♠ A 3 2 | ♠ 10 9 6 | |||

You | ||||

♠ K J 5 |

- Fourth-best leads

The practice of leading the 4th-highest card from a 4-card holding or longer. - Rule of 10 and 12

A rule for deducing declarer's holding after partner makes a 3rd or 5th best lead in a suit.

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