The functional lines emanate from the arm lines and cross the torso towards the opposite outer side of the pelvis and legs. Or you can say that the route goes from the opposite side as they do not have a direction.
One of the lines crosses the front and one crosses the back, so that together they form an X on both the front and backside. A third line of this group is the ipsilateral functional line, which runs from the shoulder to the inside of the same side’s knee. These lines are activated primarily through active exercise as in sports that require a bit more stabilization, counterweight, or getting power from your opposite side.
An example is a powerful baseball throw where the thrower draws strength from the ground and then pushes power up diagonally to the throwing hand, or a tennis player’s backhand. These lines are less active in the standing position.