[Mike O]

No problem Mike: In the answer above, the way I see it, I used plane to mean plane surface. The confusing part is that even as the plane surface rotates (think forearm rotation), and the plane surface approaches parallel to the inclined plane surface the edge also stays parallel at all points. There is little significance in the fact that the edges stay parallel at this point in Mathew's exercise, but I think he has yet grander plans for us. The fact that the edges stay parallel means that you can utilize this plane as a reference plane, a place to compare other variables, not directly related. Like wrist cock, and forearm rotation. ( fog slightly thinner now, sir)

As to a definition; Mathew's definition as I understand it is that jen's plane is simply the plane in which the left wrist hinge pin lies. Directionally, this plane is oriented along the approximate centerline of the left forearm. Functionally, it is a measure of the degree of rotation of the left forearm relative to whatever plane you choose (IP, Ground or vertical thereto)

Hope this helps, it helped me just by writing it.
G2M

OK- I feel as if I can get somewhere with your explanations.

So Jen's plane is 90 degrees to the plane of the flat left wrist- the "plane of the left wrist hinge PIN. So at low point assuming the back of the flat left wrist is facing the target- then any MOTION of the cocking left wrist would be straight up and down and the actual hinge PIN would be parallel to the swingplane.

Have I understood you correctly on this particular point.

Thanks for the help.