CLAYTON - Sam Sheline rolls his orange Mongoose mountain bike to the lip of the precipice, nearly half his wheel poking over the edge. For even the slightly vertiginous, it's a Rocky-and-Bullwinkle, the-slightest-breeze-and-I'm-history moment.

He peers over the edge: There's a sharp 9-foot drop before the trail reappears, sloping to the valley floor about 25 feet below.

The 17-year-old senior at Durham's Jordan High makes a quick assessment, turns and pedals 15 yards back into the trees, turns again and this time rides off the edge into space. There's a moment or two of silence, followed by an authoritative "whump!" -- the sound of a successful, upright landing.

Not far from where Sheline lands here at Legend Park, Allen Tutt flashes the grin of a proud father, which he is. Not of Sheline. Of the jump.

Tutt, who lives a couple of minutes away, is one of about a couple dozen volunteers responsible for building more than 80 miles of singletrack mountain bike trail in the region. What makes Tutt unique is this: While the others have strived for nice trail to ride on, Tutt wants you to ride above his.

His thing is catching air.

"Trust gravity," says Rob Williams, a 38-year-old systems administrator from Clayton, who moments later peers over the same drop. "Trust your bike," he says, reviewing the mantra that enables him to ride Tutt's various creations. "Roll it. Let gravity do its thing."

And, Tutt add, "Don't touch the brakes."

In 1993, when the Triangle's first singletrack mountain bike trail -- trail basically wide enough for the bike and not much more -- opened at Lake Crabtree County Park in Morrisville, no one was quite sure what to make of this new sport that had descended from the hills north of San Francisco.

Locally, the sport would go very slowly over the next 10 years. A second legal singletrack network didn't open until 1999, at New Light on Falls Lake.

In summer 2002, Tutt approached Clayton's director of parks and recreation about a 24-acre, vegetation-choked piece of undeveloped land at Legend Park.

By the following spring, Tutt had blazed a little over three miles of trail on the land, including a nice rock garden and the Triangle's biggest log stack, about 5 feet at its apex.

A second phase, including the hucks described earlier and a massive ravine, where the only hope of climbing up the opposite side is laying off the brakes on the ride down, followed.

Phase three opened a year and a half ago and included several wooden structures -- a sky bridge and a two-foot-wide ladder bridge that sits three to five feet off the ground and runs 85 feet through the forest.

And with that, the Triangle was about to embark on a freeride.

Legend's success -- meaning the park's stunts didn't result in a rash of serious injuries -- had a ripple effect. Lake Crabtree, Harris Lake County Park, the South Loop of Falls Lake's Beaverdam area and the Little River Regional Park beefed up or added singletrack trails.

Freeriding, as the sport is called, has taken off nationwide, according the International Mountain Bicycling Association. That's due in part to the freeriding community's growing interest in developing trails.

Locally, the Triangle Off-Road Cyclists association has been behind much of the recent change at Harris Lake and Lake Crabtree.

It's hard to gauge the size of the freeriding community, locally or nationally. Tutt says he just knows that more and more cross-country riders are showing up at Legend and undergoing freeriding's curious initiation.

"It took about a year of staring at it," Beau Warsham of Garner says of his initiation into freeriding. Specifically, the 25-year-old N.C. State student is referring to taking the plunge over The Gap, the 25-foot huck Sam Sheline rode earlier. "It's a mental thing."

Boy howdy, concurs Ian Galdy, Sheline's riding buddy. Galdy, also a 17-year-old senior at Jordan High, took a bad spill on a jump last September and has been slow to climb back on his aluminum horse.

"I might try it today," he says peering over The Gap. "It gives me the heebie jeebies."

Galdy does offer practical advice for the first-timer: Take your mountain bike to a BMX park first and practice jumping the tables -- jumps with elevated dirt areas between take-offs and landings. Jump onto the table first, then work on jumping over -- or gapping -- it.

"The key for any stunt," advises Tutt, "don't look at anything other than what you're doing."

"Stay focused," he adds. "Stay strong. If there's a question in your mind, you're not going to do it."

Anyway, adds the 37-year-old father of two with a mischievous grin, "Pain is temporary. Glory is forever.

"And to that," he says before pushing off down a roller coaster, "I'll add, 'Woo!' "