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 and 12 is used if the lead is the third best. The Rule of 11 applies when the lead is the 4th best. 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.