What Is Grounding A Club?: Dustin Johnson Penalty Raises The Question

What is grounding a club?

In the wake of Dustin Johnson's tournament-ending penalty at yesterday's PGA Championship, many fans are curious.

The rule, according to the United States Golf Association, states [Emphasis added]:

...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;

Johnson was not ignorant of the rulebook; according to the golfer, he couldn't see that it was a bunker.

"I just thought it was on a piece of dirt where the crowd had trampled [everything] down," Johnson told reporters after the incident.

Johnson's explanation notwithstanding, one sports blog has contended that he was "clearly standing in what was defined as a bunker."