Rule of 10-12

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In contract bridge, the Rule of 10-12 is applied when the opening lead is the third or the fifth best from the defender's suit. By subtracting the rank of the card led from 10 or 12 respectively, a defender can determine how many cards are higher than the card partner has led. Ten is used if the lead is fifth best [1] and 12 is used if the lead is the third best.[2] The Rule of 11 applies when the lead is the 4th best.

When following the Rule of 10-12, the lead is the third card from a three or four-card suit and the fifth card from a five-card or longer suit. Leading the third best is also applied to interior sequences (K J 10 x x) which is less ambiguous than the top of interior sequence. The third best lead from an interior sequence is called a coded 9 & 10 lead.

Sometimes opening leader may choose to lead the fourth best card from a four-card suit against a notrump contract if the third card is a spot card. The spot-card lead may give declarer a trick that he can't get if the fourth best is led.

Q 6 5 4
K 9 7 3 W    N↑ S↓    E A 10 2
J 8

If the opening lead is the 7, the suit will be blocked and defense is unable to set up the 3rd winner in the suit.

Variation[edit]

Possible variation that helps giving count from 5+ cards suit is leading the third best from even number of cards and the lowest from odd number.

See also[edit]

References[edit]

  1. ^ Rule of 10 at the BridgeGuys website
  2. ^ Rule of 12 at the BridgeGuys website