SLIPPERY ROCK — Physically and mentally, it is one of the toughest things to do in golf.

Slippery Rock High senior Brett Rinker was unfazed, however.

Rinker and a field of 25 golfers played 36 holes in one day at the USGA Junior Amateur Sectional at Somerset Country Club Tuesday.

One spot in the USGA Junior Amateur Championship was on the line and Rinker emerged as the only one in the field to shoot below par with a 3-under 141.

Rinker won by five strokes to punch his ticket to the championship tournament, which will be held July 16-21 at the Golf Club of New England in Stratham, N.H.

“To play 36 holes in one day, it’s pretty tough,” Rinker said. “You have to be physically ready and mentally ready, because once you start getting physically tired, that’s when you start getting mentally fatigued and start making mistakes.”

Rinker, though, had little trouble negotiating the rolling hills and the length of the Somerset course.

“I knew if I played two solid rounds of golf, which I knew I could do, I could win it,” Rinker said. “I felt pretty good.”

Rinker worked hard in the weight room to get physically stronger and has tacked on 20 yards to his tee shots since the fall.

Rinker can now hit a ball 270 yards in the air off the tee — which came in handy on the 6,660-yard Somerset course.

“My ball striking was really good,” Rinker said. “It’s a lot easier to hit a green with a wedge than it is with a 7-iron.

“I’m always working on my game,” Rinker added. “There are things you can always do better. All those hours I spend on the course keeps me going.”

Another change Rinker made to aid his game was a switch in putters.

He was struggling mightily at times on the green until he went to a Belly Putter — a club that extends much higher than a normal putter and is nestled in the stomach for more stability.

“I made some putts (Tuesday), but I missed some, too,” Rinker said. “I’m still working on it. I spend hours working on my putting.

“The Belly Putter has made a big difference,” Rinker added. “Your hands shake less and you are more consistent putting with it.”

Rinker said he is playing the best golf of his young life right now.

He picked up the game as a toddler and won his first tournament when he was 8. He’s no stranger to pressure-packed tournaments.

But even he admits that the USGA Junior Amateur Championship is his biggest challenge to date.

In New Hampshire, he will square off against 100 of the best junior golfers in the country.

“To win it would be the most amazing thing ever,” Rinker said. “I’m just going to go out there and enjoy myself and try to play the best golf that I can.”