Yes, this article is being written from the perspective of a right-handed golfer. If you are a lefty, then please turn the orientations around.

When the flat back of the right wrist/hand bends backward toward the forearm, this is called the right hand flex. This is different from cock - uncock which is a movement of the thumb in a flat plane in the direction of the forearm.

The right hand flex can be used in two different ways - passive or active.

As a passive element, the right hand flex is used to increase resistance to deceleration described in a previous report. The resistance to the slowing down of the club head thru the ball can add 10 to 25% more distance to the shot. So it is not to be underestimated.

In addition, as a passive element, you can use the right hand as the last small correction control for clubface control and distance control. If you do not plane to use the right hand flex in a shot, but notice that something is off - not enough power from your body turn for example - the right hand can still compensate by adding the missing power to still make the shot a success.

So, plan to hold the right hand in reserve only for when it is necessary. Also, as a passive support, you can use the right hand with the same feeling as in throwing or hitting a ball. There is a natural eye / hand coordination that can be used to your advantage for being more sensitive to your shot's distance and direction.

As an active element, the right hand flex offers the opportunity to give an additional "hand slap" to the ball at the moment of impact or just after impact. The most well known player at the moment using this technique is Michelle Wie, the young sensation from Hawaii.

If your right hand were a door, then the active right hand movement is like the slamming closed of a door.

The active right hand can be difficult to control and is not to recommended for every golfer.