Check shaft points at or inside the ball at arm parallel
As a backswing checkpoint, the instructor draws a straight line down the shaft at right-arm parallel for a lefty (left-arm parallel for a righty). For most players that line should point at the ball or just inside the ball, not way outside toward the quad. He presents this as the position he wants to see for most players.
Channel: Club Champion
Watch official source at 2:34Why this context matters
Given while reviewing the student's halfway-back shaft position on video.