The secret of the tight roped forearms

Hogan mentioned that the forearms must be so tight and solid that nobody can pry them apart.  He however forgot to mention why this is necessary for the golf swing.  However from my experience, what is necessary is the left arm is suppose to be stiff and the left wrist and hand must be balancing the club with the left pad and left forefinger.  The purpose of this is to "measure" how far the ball is from the body... meaning it is the part of the swing that ensures that we do not dub the club to the ground.  It is the part of the swing that ensures that the distance between the shoulders and the ball are kept the same throughout the swing.  This is particularly necessary when chipping because we tend to bend out left arm when addressing the ball resulting in a dubbed chip.