The line in 6-b-3-0-1;
" AT RIGHT ANGLES TO THE LEFT ARM PLANE."
Seems. applicable to angled hinging-BUT- not horizontal or vertical(the dual hinges)
if, what is meant by LEFT ARM PLANE is the plane of entire primary lever assembly.
#3 remains on the plane and traces the line. The left arm wedge is perpendicular to the plane continuously for angled hinge only. And #3 roll on the shaft because the clubface and clubshaft are independant for horizontal and vertical hinging ??