[Andretti]

Many times in the book, in various posts here and most of all in the flying wedges clip there are references to tracing the plane line. It seems both an important and useful concept.
Problem is I'm not quite sure how to use this information...

For a straight shot: am I supposed to 'follow' the plane line, parallell to the stance line, on the ground with the first joint of my right index finger?
If yes- what does follow mean? My hand will obviously move backward, inward and upward.. What is my visual reference?