What is Grounding a Club

What is grounding a club, really? Yesterday, golfer Dustin Johnson was penalized at the PGA Championship for grounding a club.

The rule, according to the United States Golf Association, states:

…before making a stroke at a ball that is in a hazard (whether a bunker or a water hazard) or that, having been lifted from a hazard, may be dropped or placed in the hazard, the player must not:

a. Test the condition of the hazard or any similar hazard;

b. Touch the ground in the hazard or water in the water hazard with his hand or a club;

Dustin Johnson said that he couldn’t see that it was a bunker.