Shallow the driver by moving lead hip and knee forward
Craig Hanson teaches that from the top of the driver swing you feel the lead (left) hip and lead (left) knee move forward, and that this lateral movement of the lower half with a slight arch of the back helps shallow out your swing plane. To train the feel, get up to the top and feel that initial forward move of the lead hip and knee, almost like having your hands on a wall and creating a bit of a stretch.
Channel: CraigHansonGolf
Watch official source at 1:20Why this context matters
From a driver lesson framed around copying tour players' swing geometry.