[Bagger Lance]

Bagger thanks for your valiant attempts to help me understand. I read all the posts, i've seen the pics in the book. But i still can't understand how you can aim your hands to a point on the low point plane line, when it's underground and you can't see it.

The internet has never been the best place for communications and I'm certainly not the best at communicating in general, so lets keep going.

You don't have to treat the low point plane line as something under the ground from a visual standpoint. The equivalent line is on the surface of the ground. Its a two dimensional line right next to the target line, but just outside of it. Since your eyes are not in the plane itself but well above it, you can visually treat the low point plane line as a separate line.
The only time the clubhead is concerned with the low point line is at low point. ( what a deep thought. Told you I wasn't a good communicator) You will contact the ball on the target line but the clubhead will continue to the low point line, touch it for an instant and then move back up plane.

Back to topic -

From the top of your swing, mentally draw a straight line from your right index finger to a point on the ground in front of and just outside the center of the ball. Take your karate chop/lag pressure all the way down the line to that spot with quiet hands. The point you select to aim at really depends on the club selection and your hand speed. So experiment with it and move the point backwards or forwards until you locate what is right for you.