why straight?

[nevercrosses]

For Horizontal Hinge Action (Ideal Compression), the Clubface is Open at Impact and Square only at Separation (1-L #17).

And, using approximate 'clock' terms, the Center of the Ball is at 7:00 at Impact and at 6:00 -- and precisely On Line -- at
Separation.

Study 2-C-1 (Linear Force -- The Ideal Application) and Sketches 2-C-1 #1, #2A & B and #3.

Thank you again.

I need to work on my terminology. All of those impacts should have said separation.

Now that I have looked at 2-C-1 #1, #2, #2b and #3 in more detail, it is more clear than ever that the striker is moving to the right. One would certainly have to point this to the left to create a straight shot if hit before low point.

It looks like HK was pretty darn close to describing the D-plane in pictures.