[Daryl]

First Knuckle.

The First Knuckle is the "Turning Point" (Center Point, Leading Point) of the Right Forearm Flying Wedge.

A Beam of Light down the Right Forearm, through the First Knuckle will Shine on the Plane-Line. A Beam of Light from the First Knuckle through the Sweet-spot of the Club Head will Shine on the Plane-Line.

Both Beams of Light need to be shining On-Plane at least through the Impact Interval to have a 3 dimensional Impact.

(I think that's correct).