When we lead against a NT contract it is necessary to know when partner makes a lead that the J lead has no honor higher. Many a time we are uncertain whether the lead is from AJ1065 or J10975? Or KJ1065 or J10853? Knowing that the Jack has no honor makes it so much easier to control our defense.
Therefore we lead the Ten if we hold AJT65 - not the Jack! KJ1065 or K10976
Remember : The Ten must be supported by the Jack or the 9 and a higher honor. This is a partnership arrangement. But gee , does this make it easy!!! Fourth highest from longest and strongest does not apply.