"Jack Denies, Ten Implies" is a lead agreement whereby the lead of the jack always denies a higher honor, but the 10 or 9 "implies" two higher (non-touching) honor. This convention is also known as '0 or 2 Higher' leads, or coded 9's and 10's.
This convention is used when holding interior honor sequences headed by the jack or ten: AJTx, KJTx, AT9x, KT9x, QT9x, etc.
Normally, the top interior card from these sequences is led:
Playing 0 or 2 Higher Leads, however, the third-highest card is led instead:
Thus, the lead of a ten or nine suggests "0 or 2 higher" cards. It may be from one of the above sequences (i.e. 2 higher cards), or from the top of a sequence such as T98xx (i.e. 0 higher cards).
- JT84 - lead the jack, which denies a higher honor (i.e. the queen, king or ace).
- JT974 - again, lead the jack.
- KJT4 - here you lead the 10. Leading the jack would deny the king. The 10 shows the jack plus a higher non-touching honor, i.e. the ace or king.
- AJT65 - lead the 10.
- KT94 - lead the 9 to show 0 or 2 higher (non-touching) honors.
- QT987 - again, lead the 9.
- 0 or 2 higher leads apply on opening leads as well as subsequent new suit leads.
- 0 or 2 higher leads only apply when leading from a tenace. From an unbroken sequences such as QJTx, for example, the top card should be led.
- 0 or 2 higher leads do not apply when leading from AJTx or AT9x against a suit contract. In those situations, the standard lead is the ace.
In his great book "How to Defend a Bridge Hand", the late Bill Root (expert player and writer) strongly endorsed 0 or 2 higher leads, saying:
"This convention should be used by all competent partnerships. The advantage of Zero or Two Higher is the card you lead makes it easier for your partner to figure out whether you are leading the top of a sequence or from an inside sequence." 1
American expert Larry Cohen, however, is less enthusiastic:
"This is very good against weak players as you give your partner a useful piece of information. Meanwhile, a poor declarer won't appreciate the inferences available. On the contrary, against good players, this is a horrible method. It gives way too much of an advantage to a decent declarer.
"I'll let you in on a Bergen-Cohen secret: We used to play this 10/9 0 or 2 method against weak players, but standard against good players. We had 2 different convention cards depending on who our match that day was against. Thank goodness, our opponents never knew our criteria!" 2
1 Root, William S (1994). How to Defend a Bridge Hand.
2 Cohen, Larry. "Opening Leads".