This is based on a training aide I spotted on TV. It’s intended to mount to the shaft of your golf club. I would recommend clamping it on toward the head of the club and then sliding it up the shaft as desired. It has holes for M6 threaded inserts and bolts so it can be tightened in place.
To use it, once you have it on your club. Set an alignment stick right up against your toes, with the side with the arrow faced up and towards your backswing direction. To the right for a righty and left for a lefty. The objective is to keep the arrow pointing to the stick as you bring the club back. At most you’ll be bringing it back a couple feet. The intention is to keep the hands inside while the club head stays outside. Repeat this 2 foot section of the swing until the cows come home for a perfect takeaway.