[Dariusz J.]

Jeff or anyone else,
I'd be interested if someone could clearly clarify for me what is meant by open and closed in relation to the swing arc. If at impact the left wrist is cupped then the face closes. If at impact the left wrist is arched the face is open. So how does the left wrist moving from cupped to flat at the top of the swing- create a closing motion of th clubface? Never understood this and I have never heard a reasonable explanation- look forward to understanding your perspective.

Mike, a square-to-the-arc clubhead means that the clubface is perpendicular to the swing arc. The forearm rotation clockwise during backswing opens the clubface in relation to the arc; the same rotation but anti-clockwise brings it to the square position during downswing and closes it in the follow through.
Now, depending on the release type, some golfers brings the clubface square earlier and some later just before impact. The same may happen after impact - some golfers maintain the clubface square after impact (those who swing left with a late swivel) and some close it rapidly just after impact together with a crossover of their forearms (early swivel).
Hogan delivered his clubface square already before entering the impact zone and maintained it square long after impact what is one of very suspected "culprits" of his overhuman accuracy and repeatability.

Cheers