When reading 2-C-1#1 remember that the Impact interval has been extended to Low Point (Homer has this statement in the first paragraph). Does that clear things up?
How you can trace either the impact line or the low point line since the ball could be located at low point, thus no difference in line.
The Impact Plane Line and the Low Point Plane line reside on the same plane as shown in 2-C-1#1. The Low Point line is further down the sweet spot plane (lower) thus it presents a 2nd line outside the impact line when represented on the ground.
I probably haven't explained this very well, but if you look at 2-C-1#1 and keep in mind the extended impact interval to Low Point, it should clear it up (I hope).
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