Pull the trail shoulder down to reconnect the arm
From the top of the downswing the trail shoulder lowers and pulls down so the trailing arm (tricep) reconnects to the ribs, storing speed and angle for cleaner contact. Hanson says over 95% of amateurs instead make a slight lift at the start, so the arms never reconnect, producing a wide downswing with fat and thin shots.
Channel: CraigHansonGolf
Watch official source at 0:20Why this context matters
Hanson frames this as the 'magic move' the modern downswing is built on.