We are all built so differently, not only physically but neurologically. If you try swinging like Hogan and are built like Davis Love, it won't work. All of the necessary information is in the yellow book. It is finding the right pattern that is tough. For that, an instructor that knows, ie, the ones that typically are on this site, must be consulted. I recently took two lessons from a top 100 guy who will remain nameless, as he is a good guy and has a great rep. The first lesson focused on a hitting motion of the right arm during the swing, axe technique, the second he weakened my grip and worked on a startup swivel. These are two different feels, let alone patterns. He does not teach the golfing machine and uses these in his bag of tricks, but it left me with an unclomfortablefeeling, to say the least. Teaching aids like Jeff's are important because without access to an ai, for some of us it is the best way to feel the changes we need to make.