Fix your grip: get the bottom hand on top
Feel the top hand running in the fingers so that looking down you see two to two-and-a-half knuckles. If the bottom hand sits too far underneath you can see its thumb; in a good grip you should never see that thumb and should be able to cover it. Move the bottom hand more on top so the hands work as a unit, because when the hand is underneath it is very difficult for the wrists to function properly in the swing.
Channel: Dan Grieve
Watch official source at 14:07