Rate of closure is how we describe how much the club is rotating during the downswing, impact and follow through. In the past closing the club right at impact was taught as a way to increase distance. We have since learned this is not the case.
It is a more modern belief that the lower the rate of closure the better the player. Better players are getting the club more square on the downswing eliminating the need to decelerate the club to square the face up at impact. This also changes the look of the follow through.
This does not mean that you should not use your wrist. There will still be some rotation in the wrist. What will need for power and consistency is flexion and extension at impact.
The extension is the wrist moving away from the forearm. If you hold your forearm horizontally in front of you, point your thumb vertically. Now get the extension by extending your thumb away from your body.
The second wrist motion is flexion. Hold your palm facing the ground with your wrist flat and forearm flat. Take your knuckles and move them up and towards the back of your forearm. This is extension. Do the opposite with your knuckles moving towards the part of your forearm without hair, the front and you have flexion.
A great deal of power comes from these two wrist motions with very little coming from rotation of the wrist. It was said that Moe Norman had the least amount of wrist rotation and that could be the reason he was one of the best ball strikers ever.
Here are a couple of links where you can learn more about rate of closure;
http://forum.brianmanzellagolf.com/golfing-discussions/14607-measuring-rate-closure-3.html
https://www.gearssports.com/gears-golf-club-ball-metrics/
https://www.philcheetham.com/workshop/
Jim Hartnett, PGA
