[Mike O]

Mike; "Lines of Intersection" (with the wall). Of course these will be parallel. Any two lines, starting parallel to one another(the book edges), when extended to infinity, their lines of intersection with a common plane (the wall) will also be parallel.

In your example, you are thinking of the surface plane of the book cover, not the line or edge of the plane When the plane of book cover 1 and the plane of book cover 2 intersect a common plane, like the wall, each transcribes a line. These two intersections will be parallel to one another, even though the direction of the two book covers approaching the plane (wall). Try it for your self. Take a hard v=cover book and hold it against a solid surface that you can write on. Hold the book open to the amount of your choice and while hilding it in that position, trace the edge of the book cover where it touches the hard surface. Try it several times, at different amounts of open or closed. The tracings will always be parallel.

G2M

G2M,
I understand your post- thanks. So the edge of the front book cover and the back book cover edge, as they touch or run through the wall - whether at an angle or when both surfaces are parallel to each other- create lines on the vertical wall that are always parallel to each other- even when the plane of the covers are not- that is when the "up and down" angle of the planes are different for the two- they both still create parallel plane edges on the vertical wall. Now, if the plane angles are not the same "side to side" and they go through the vertical wall then those plane angle edges will not be parallel.

Now, could you make another post and just tell me what edge of the swing plane and what edge of the #3 accumulator plane are parallel? I'm afraid of looking back at all of the other posts-as I have a fear of fog! So don't worry if your answer is really simple- cause that's actually what I'm looking for.
Thanks,
Mike O.