[Yoda]

I thought the vertical hinge was perpindicular to the plane, not parallel to
ground and that the horizontal hinge was parallel to the plane not
perpendicular to the ground. I thought the reference point was the plane, not
the ground.

The Hinge Pin is always mounted perpendicular to one of
the three basic Planes of Motion, i.e., horizontal, vertical or angled. The
Hinge Blade always rotates in a circle about its pin and remains
perpendicular to that Plane as well. This is simply how a hinge operates,
i.e., it is the action of a hinge.

In G.O.L.F., the Hinge Actions are named for the Plane of Motion imparted by
the Hinge Blade. They are not named for the always
perpendicular Hinge Pin. For example, a pin mounted perpendicular
to a horizontal plane produces a horizontal blade motion and is therefore
termed Horizontal Hinge Action. Similarly, a pin mounted perpendicular
to a vertical plane produces a vertical blade motion and is termed Vertical
Hinge Action. The same logic holds for Angled Hinge Action.

To clear the Fog, take a pencil and position it perpendicular to the cover of
a book. Maintaining that perpendicular position of the pencil, lay the
book first horizontally; then stand it vertically on its end; and finally
tilt it at an angle. Note that no matter what the plane of the book --
horizontal, vertical or angled -- the pencil remained perpendicular to
the book.

Now, substitute a hinge for the pencil. Like the pencil, the pin is always
perpendicular to the surface of the book. And the rotation of the blade
around its pin is always the same, no matter how you position the
book. Only the Plane of Motion differs, and it is on that basis that the
Hinge Actions are classified.