Get the trail knee to the finish line before the hands
Craig Hanson calls the number one downswing checkpoint getting the trail (right) knee to the finish line before the hands do, and presents it as essential to having any chance of becoming a solid ball striker. He contrasts this with amateurs, whose hands are 'winning the race' with a big gap between the knees and no shaft lean. He offers it as a checkpoint to see whether the downswing is moving effectively.
Channel: CraigHansonGolf
Watch official source at 1:43