[Mathew]

Not sure I got the full meaning of the graphic, but what I see is the red plane representing the perpendicular(to the plane of the left arm assembly) plane of the left wrist hinge pin, so the motion would be horizontal/parallel to the inclined plae of the left arm assembly until the swivel starts, and then the red plane would have to rotate to the finish position. Of course I could have completely misunderstood the graphic entirely.....

G2M

Getting warm with one part "what I see is the red plane representing the perpendicular(to the plane of the left arm assembly) plane of the left wrist hinge pin"

The left arm does a play a role in finding this third plane..

Just keep thinking about geometrical alignments and relationships - this is what this thread is all about and trying to get you to think 'out of the book' and start taking Homer Kelleys alignments and understanding them....