[O.B.Left]

Thanks to Homer for getting it right when he says no hand effort toward the target, but no thanks to Hogan for his misleading 2HBP illustration in 2L, which 99 of 100 readers will take to mean a horizontal hand/arm effort through impact, i.e. steering, disrupting impact alignments, stifling CF, and distorting the arc of the clubhead.

Here's the part of the book I believe you're alluding to. Ive taken the liberty of bolding the particular sentence of interest.

CHAPTER 2 STATEMENT OF PRINCIPLE

PAGE 34

THE FLAIL

If thrust is applied only to the Left Arm (Handle), the Clubshaft (Swingle) will perform more like a Rope Handle (rising Clubhead pull), but if prestressed by Clubhead Lag Pressure Point pressure, more like an Axe Handle (steady Clubhead Inertia). However, the Primary Lever Assembly is only somewhat flail like. That is, it is bolted together as with a hinge pin, rather than tied together with a thong, so that it can only be “Cocked” and/or “Rotated” per 4-B and 4-C and cannot pass the “Handle” (4-A-2) while moving toward full extension per 2-P. This insures the Imperative Flat Left Wrist (1-L, 2-0). Study 2-F, 6-F-0 and 10-19. As with the standard flail, the true and proper direction for its mass to move is “downward On Plane” regardless of the incidental appearance of moving “forward On Plane.” Always from the Top. This is indispensable for both Hitters and Swingers for inhibiting Clubhead Throwaway. Study 2-K and Chapter 2-P.