It's called a rake.
This isn't the garden variety rake, but a wooden one with tines that are 2 1/2 inches apart. Nicklaus ordered 150 of them for the bunkers at Muirfield Village, then made a slight adjustment so they would be more potent.
“As I was testing them on Saturday, I found that once the bunker was raked the second time, the rake was too narrow and it just went right back to a smooth bunker,” Nicklaus said. “So I said, ‘Let's take every other tooth out.”'
The rakes create furrows in the sand, so the ball will sit atop a slight ridge or nestle between them. It makes it difficult to get any spin on the ball, therefore making it tough to get the ball close to the hole.
OK, so it's not as high-tech as titanium, not as sophisticated as sub-air pumps.
Still, the gap-toothed, wooden rakes being used this week at the Memorial might be enough to bring scores down, or at least make world-class players think twice about hitting into bunkers.
And that's the whole idea of a bunker, isn't it?
Nicklaus has designed hundreds of golf courses around the world, and he could think of three reasons why an architect would put in a bunker - it looks nice, it helps define the shape of the hole and it penalizes an errant shot.