Rule of 10 & 12

Similar to the Rule of Eleven, the Rule of 10 is for 5th best leads and the rule of 12 is for 3rd best leads. 

                 Q86

K7543                   JT9

                A2

West leads the 3, 5th best.  10 - 3 = 7 better cards in the other 3 hands, so East knows who has the King.

               Q86

  T742                  KJ53

               A8

West leads the 4 vs a 4  contract.  12-4=8 better cards in the other 3 hands, so East knows that declarer South has at least 1 more club in his hand, so the King is cashing and will not get ruffed.

See also:  Rule of Eleven

Compiled by Lorne Russell 2005