Rule 23 of 25 · Chapter IV — Numbers, Lies, and Greens
From thick rough, take one more club, grip firmer, and accept a steeper strike with less spin.
Why this rule exists
Grass caught between the face and the ball kills spin and grabs the hosel, so the ball comes out lower, turns the club shut, and runs on landing. A firmer grip resists the twist and a steeper angle of attack gets to the ball with less grass in the way. Planning for the flyer and the lost control beats being surprised by it on the green.
In practice
Set the ball a touch back, stand slightly more open with a bit more weight forward, and swing down more sharply with a shorter backswing than usual. Hold the grip tighter than normal, especially with the lead hand, and commit to swinging through the grass rather than at the ball. Then aim for the front half of the green or a spot short of it and let the ball chase.
When it doesn't apply
When the lie is so buried that you can't reach the back of the ball cleanly, forget the green — take a wedge, aim at the fairway, and get out. Fluffy rough where the ball sits up on top of the grass plays more like a tee shot and often needs less club, not more.