Once you understand the connection of the left arm, I think it's important that you understand the role the left arm plays in the golf swing and I think people have been mislead forever in how the left arm travels and what it does.
First of all, through teaching golf over the years, you always try to find the simplest ways that people relate best to the golf swing or to a feel. One of the feels that I found that really helps people understand the golf swing is the feeling of keeping the left elbow always pointed down to the ground.
Ben Hogan's Five Fundamentals
Again, in Ben Hogan's five fundamentals, he drew a picture of the left arm and how it worked, and he drew the picture of the left arm set at the top, and he drew the picture of the left arm traveling this way. And he described that as feeling like you thumb a ride, and I thought that was really a good way to describe it and what I want you to understand is this clubface is controlled actually by your left elbow.
Elbow Position Affects Clubface Angle
If my left elbow rolls here, look how that changed the clubface, look at the angle that created. And not only when the left elbow rolls here does it change the clubface, it changes your radius, and it changes your arc. So the idea is if you keep your left elbow down, look how your arc stays the same, look how the face of the club stays the same and the radius of the golf swing stays the same.
This can be done by simply connecting the left arm to your shoulder, feeling that you hold a handkerchief under, and by the simple feeling of keeping your left elbow down going back and your left elbow down going through. That's exactly the way Hogan drew in his book, the way the left arm traveled. And anytime the left arm changes it changes your radius, it changes your arc, creates an angle.
We don't want any angles in a golf swing, we want to always maintain the club square, square, and square. And it can't do that if the elbow comes out or if the arm changes and changes the radius and changes the arc. So one of the feels we use in our teaching all of the time to understand part of connection once your set-up, is the constant feel of the left elbow down. We never want the left elbow out.