There are plenty of theories and ideas about the swing plane. By searching the web for the words “swing” and “plane” you can find many articles. We found the following information very informative:

The following information comes courtesy of John Dunigan of http://www.golfbetterproductions.com.  Please note that John Dunigan does not personally endorse the swingplane^(TM).

The Swing Plane Concept
Using the shaft angle at address (lie angle) as our guide, we cut a semicircle out of a 4'x 8' piece of plywood, giving a flat surface that we can slide the club shaft along without changing its original angle. This board represents the plane that the club would travel along when swung according to its lie angle (intended design). We know the board as the plane board.

The Plane Truth
Looking at the photos from left to right:

Address: Starting out with both the club shaft and my hands on-plane (Plane A black).
Half Way Back: Club shaft, hands and right forearm are on-plane.
At the Top: Club shaft, hands and right forearm have shifted to a more vertical, over-the-top of the original, plane (Plane B, white line). Only the right elbow remains on-plane. Herein lies the difficulty with the golf swing: getting back down to the original plane. Whatever you do to start the downswing must return the club to the original plane.
Start Down: Moving the hands and club shaft back toward the plane--not toward the ball, is the easiest way to get the club back on plane.
Half Way Down: Club shaft, hands and right forearm are once again on-plane. It's easy from here.

The Two Plane Swing Every golf swing has a section that is over-the-top of (or above) the original plane. To make the backswing long enough to create sufficient club head speed to play the game, we must shift above plane. Unfortunately for our understanding of what happens in a golf swing, this shift is built into our body and so we don't even notice it. Obviously, since we don't notice the shift, we don't realize the need to return to the original plane. What makes the move back to the plane so difficult is that it feels like we are swinging away from the ball. Intuitively, from the Top of the backswing, we try to swing right at the ball, because we don't realize that a plane shift has occurred. It is the transition (what you do at the start down) that will make or break you. Ben Hogan called it a "crossroads." If you take the wrong road, you can't get where you want to go.

Once you become aware of this plane shift and realize that you must correct it before you head for the ball, the golf swing becomes much easier to understand and make. All the myriad theories of how to start the downswing fall by the wayside because they can't possibly result in returning the club to the original plane. This is why the average golfer hasn't improved in years: For years, golf instructors have taught us to start the downswing in a way that makes it difficult, if not impossible, to return the club to the original plane. In short, that can't work. That's why I started writing books: At the very least, if you do what I tell you, it will work!

Copyright © John Dunigan 2003. All rights reserved.

LIE ANGLE ~ The swingplane^(TM) adjusts to all lie angles.
Lie angle is the angle created by the centre line of the shaft and the horizontal grooves on the clubface. The same lie angle does not suit all players. Physical differences like your height and arm-length may dictate a different lie angle for you. Proper lie angle is essential to achieving consistently solid, accurate shots. It is physically impossible to hit a straight shot with a square clubface at impact if your lie angle is incorrect. If your lie angle is "toe up," you'll tend to hit the ball from right-to-left, and will benefit from a flatter lie angle; if your lie angle is "toe down," you will have a tendency to slice the ball, and will benefit from a more upright lie angle.

To find out what kind of lie angle you require, consult a PGA Golf Professional and club-fitter, who can determine if you would benefit from a flatter or more upright lie angle. When you play with clubs whose lie angle fits your needs, you'll hit straighter shots.

	What’s the lie angle of your club? If you are not sure, contact your local PGA Golf Professional or the manufacturer of your clubs. They should provide you with details. The Lie Angle is an angle (4) developed by shaft centre axis (3) and ground viewed from face side. You can adjust the swingplane(TM) to the correct angle (3).

Basics of Golf
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