This combination can be held in four different ways:
+-----------------+-----------------+
| _In One Hand._ | _In the Other._ |
+-----------------+-----------------+
| A K J | x x x |
| A K x | J x x |
| A J x | K x x |
| K J x | A x x |
+-----------------+-----------------+
With the first arrangement of this combination the lead should come
from the weak hand and the jack should be played. In the second the
jack may be led from the weak hand toward the ace king; although
unless you also hold the ten, little can be gained by this play, for
if the adversary covers the jack with the queen, as he should, the
ten will be established against you. In the two remaining cases a low
card should be led up to the jack.
With each of these combinations, unless you hold nine cards or more
in the combined hands, the finesse should be taken.
With ace jack in one hand and the king in the other, or with king
jack in one hand and ace in the other, unless you also hold the
ten of the suit, do not lead the jack toward the ace; for if the
adversary covers the jack with the queen, the ten is established
against you.
If you hold nine cards in the two hands it is not sound play to
finesse; with but four cards against you the queen will probably fall
in two rounds of the suit.