2-N-0 (Clubhead Line of Flight)
Clubhead Line of Flight has a lot to do with the 'Visual Equivalents' (2-J-3) and Angle vs. Arc of Approach. John Furze, GSED did a great article on Clubhead Line of Flight. Homer states that the line of flight of the clubhead and the line of flight of the ball are not the same, but touch momentarily at impact.
Homer states that the closer the ball position is to the Low Point, the steeper the angle of attack and the higher the ball flight trajectory. However, according to Trackman, if you move the ball position back the angle of attack becomes steeper which causes the ball to fly lower.
There's also talk of the right forearm motion being 'three dimensional.' The clubhead motion at impact is 3 dimensional according to TGM. This means that when the clubhead of an iron strikes a ball, it makes the first motion of going further DOWNWARD (look at it from a Face On View). After it starts going downward, the clubhead will go further OUTWARD (to the right of the plane line -- just slightly), and then the clubwill go forward as the golfer follows thru and finishes. Thus the 3-dimensional motion of the clubhead is DOWN, OUT and FORWARD. The same can be said for the right forearm as well.
Homer talks about a feeling thru impact of making an underhand pitch motion. If you don't do that, you are either way underplane (aka roundhousing) or 'Steering' which is the hands trying to actively steer the clubface square to the target thru impact. Usually steering and getting above the plane (aka coming Over the Top) go hand in hand. This is important to note as most golfers who steer their buddies will tell them that they are not releasing the club or that they need to 'get behind it' when the real problem is they are coming over the top.
2-N-1 (Force Vectors)
Vector in physics is an 'influence.' So when we are talking force vectors, we are what influences force. Homer gives us three force influences.
1. For the outward part of the 'down, out and forward' motion of the clubhead thru impact, the PRIMARY influence of the downward foces is done by the shoulder turn (swinger) or the right arm thrust (hitter). The golfer can push or swing the primary lever assembly (left arm and the clubshaft) from when they are in the hinge motion and that will suffice as an outward force vector. Here's a Lynn Blake video explaining it a little better.
2. The Primary Downward Force Vector is produced by straightening the right elbow. The hitter can just straighten the right arm out. Homer notes that this includes uncokcing of the left wrist. This is what the 'swinger' can do. They can uncock the left wrist into impact and that will straighten out the right elbow. In fact, one way a swinger can use their procedure is feeling like they are making a karate chop of sorts with the left hand down into the ball. Without a club, take your normal swing to the top and stop. When you get to the top, the back of the left hand should be facing at the 'caddy' (aka the camera if you were filming from the face on view). Now, let your right hand go and as you make your downswing feel like you are karate chopping with the left hand with the back of the hand facing the caddy. It's natural to think that the golfer would shank it, but centrifigul force takes over, squares up the clubface and then causes the face to close in the hinging action and produce a horizontal hinge.
Homer also states that you can accomplish this downward force by just dropping, pulling or pushing the lever assembly downward.
3. The 'On Plane' Force vector is done thru getting the right shoulder on plane on the downswing and that's accomplished by tilting the axis (the spine) towards the back leg on the downswing.
This is important for golfers to learn so they can accomplish the flat left wrist at impact.
If the golfer is struggling with coming over the top, they may want to look at the outward and on-plane force vectors (#1 and #3). So they may want to look at their shoulder turn (swinger) or right arm thrust (hitter) as well as their right shoulder and see if that's on plane and if not, look at their axis tilt.
If the golfer is coming down on the ball with a steep enough angle of attack, then they should look at their left wrist uncocking on the downswing (swinger) or their right arm straightening (hitter).
I feel #2 force vector is important to grasp as Lynn Blake once said about the 3-Dimensional clubhead motion, most people can get the 'out' and the 'forward' part of the 3-D motion. However, where most golfers struggle is the 'down' part, they don't get enough 'down.'
Brian Manzella has stated that the proper amount of angle of attack with a 7-iron is about -3.5 to -4.0*. When I first went on Trackman, back when I had a flip and had a high ball flight, my Angle of Attack was at -2.7*. I've seen other flippers and high ball hitters have an Angle of Attack with a 7-iron in the -0.5 to -1.0* range. Now that I don't have a flip, my latest Angle of Attack numbers were in the -3.3 to -4.1* range.
Again, that's getting enough 'down' on the ball. I believe there's other factors that a golfer needs in order to be in a position to hit far enough down on the ball, but the main concept is that most Angle of Attacks by golfers are far too shallow and they don't have adequate downward force vectors to hit the ball with precision.