Holes-in-one are hard to come by in the Masters Tournament. Since the inaugural event at Augusta National Golf Club in 1934, only 18 aces have been made on the course's four par-3s.

Trevor Immelman jumps for joy after his hole-in-one on the par-3 16th hole during the final round of the 2005 Masters. The South African had this photo framed for his office. "For that shot to go in, it was like a dream come true," he said. Only 18 aces have been made at the Masters. (Andrew Davis Tucker/Staff)

None of the 96 starters in the 71st Masters made an ace in Thursday's first round. The most recent ace came in the final round of the 2005 tournament when Trevor Immelman hit a 7-iron into the hole on No. 16.

There is no question which is the toughest par-3 to conquer. It took 58 years before anyone aced the fourth hole. Jeff Sluman, who did it in 1992, is still the only player to walk off that green with a "1" on his scorecard.

"Obviously, it is the toughest if I'm the only one who's ever done it," said Sluman, who made bogey on the hole in Thursday's first round. "It's nice to know I've done something there that nobody's done."

Sluman said jokingly that "it's unbelievable" there isn't a plaque on the hole commemorating his ace.

The 16th is the most-aced hole. Ten players have done it, starting with Ross Somerville in the inaugural Masters in 1934. Next comes the sixth hole, with four aces, the first one coming in 1954.

Only three players have aced the most famous, and shortest, of the par-3s, the 155-yard 12th hole. Claude Harmon was the first to do it, in 1947.

Overall, all the par-3s ranked among the 12 toughest holes in the 2006 Masters. The fourth hole was the seventh-most difficult with an average of 3.208 strokes, followed by No. 12 (eighth-toughest, also at 3.208), No. 16 (11th-toughest at 3.131) and No. 6 (12th-toughest at 3.124).

"They are very difficult and demanding as far as your control of the golf ball and the control of your distance; you don't just randomly get up on any of those holes and pull a club," Sluman said. "You have to think on every shot out there. You and your caddie have to determine what the right club is, then go ahead and try to execute it."

Said Kirk Triplett: "We have a number of courses where the par-3s are longer and maybe more difficult on the card, but they don't have the conditions you have at Augusta, with the winds and sometimes the greens being very firm and the landing areas are very small, like No. 12." Triplett figured it out, at least for one shot. His ace on No. 16 in the final round of the 2004 Masters helped him shoot 72 and earned him a sixth-place finish.

"At the time I was not playing to win the tournament," Triplett said. "You're playing to have a good finish.

"You can't ask for much more than that," he said of his ace, which came with a 6-iron. "It was very exciting."

Triplett, who has three victories in 18 years on the PGA Tour, called the ace "the single most exciting shot of my life."

Immelman uses a similar phrase to describe his 2005 ace on No. 16, saying it was "probably the most exciting moment in my career."

"I was in the second-to-last group, so obviously there was a lot of pressure and a lot of people there," said Immelman, who shot 73 that day and finished in a tie for fifth place. "For that shot to go in, it was like a dream come true. It's something I'll never forget."

Augusta Chronicle photographer Andrew Davis Tucker caught Immelman's reaction to the ace as he leaped high in the air. The South African framed the photo and placed it in his office.

Sluman and Immelman are among the five players in this year's field to have aced a hole during the Masters. Raymond Floyd did it on No. 16 in 1996, and Chris DiMarco (No. 6) and Padraig Harrington (No. 16) had aces in 2004.

Triplett joined DiMarco and Harrington in the "hole-in-one club" in 2004, the only year more than two aces have been recorded. Also that year, Harrington and Triplett scored their aces on No. 16 in consecutive groups, the only time that has ever happened.

Of the par-3s, only No. 4 has been lengthened since the course started adding yardage in 1999. It was stretched back 35 yards to a robust 240 yards starting in 2006. It played to 213 yards when Sluman used a 4-iron to make his ace there in the opening round of the 1992 Masters.

"That's probably the last time I hit the green in regulation," Sluman said. "It's such a difficult golf hole."

The hole now requires a long iron, a hybrid club or a metal wood to an elevated and elongated green that slopes to the front and is guarded by bunkers in front and to the left of the green.

Even so, Sluman doesn't think he'll be the only one to ever ace No. 4.

"With all the great players, it wouldn't surprise me this year to see a hole-in-one on it," he said. "No record is safe. With one lucky shot, anybody in the tournament can make a hole-in-one on it. You have to hit a good shot. I think Ben Hogan said a great shot is within 2 feet of the hole and it's lucky if it goes in."

"Oh yeah, it can happen," Shaun Micheel said. "There's enough guys firing balls at the green. It just takes one good shot and one good bounce and a little bit of luck."

Reach David Westin at (706) 823-3224 or david.westin@augustachronicle.com.