In the world of professional marbles games, nothing is more sacred than a player's thumb and index finger. The grip is inviolable, and its texture must not be disturbed by anything -- soap, chlorine, or, say, a fan's sweaty handshake -- or else the player could lose familiarity with his flick, and thus, could choke.

This is why yesterday, during the U.S. Marbles Championship tournament in Frederick County, as 20-year-old Robbie Nicholson was trying to quench his thirst with a soda, he needed his mother's help.

She held the can steady on a table while he used his left hand to pop it open.

"Don't do nothing with your right hand, except play marbles," said Nicholson, of Clarksburg, W.Va.

Marbles, after all these years of booming soccer leagues and fast-paced electronic diversions, is still chugging along in various corners of the world, one of which happens to be in Frederick. This past weekend's tournament at Middletown Park is touted by organizers as one of the most challenging tournaments in the world because, unlike others, there is no age limit and repeat champions can return to compete.

Some of this weekend's competitors were old-timers who had won the sport's most famous event, the National Marbles Tournament, held annually in New Jersey, when they were teenagers competing for college scholarship money. But the U.S. Marbles Championship, organized by a 37-year-old Frederick computer technician/marbles fiend, attracts a cozy group of working professionals, graduate students and high schoolers who vie for cash awards, and, not to be discounted, a sizable measure of celebrity within their intimate subculture.

The U.S. Marbles Championship typically has attracted about 40 competitors every year from such states as Maryland, West Virginia and Tennessee but in its 12th incarnation this weekend, it pulled in a little more than half that number. "It's not an easy game. There's a lot of room for error," said Jeff Kimmell, the tournament's impresario. "If you look at someone who plays marbles the right way, there's a lot of skills required. You have to have a long game, a short game, and you still have to hit the midrange shots."

Marbles at first seems like golf or pool, as players spend most of the time eyeing balls and targets, and spectators speak to one another in hushed tones. In the version of marbles played this weekend, matches pitted two people against one another. Each tried to be the first to knock 50 marbles outside the border of a concrete circle that is 10 feet in diameter.

Using their thumb and index finger, they crouched down on all fours and flicked their "shooter" -- a ball about the size of a marble but made of glass or stone -- at a configuration of marbles in the middle of the circular ring. Because only 13 marbles are laid out during each round, or "rack," games can take up to an hour, as players try to reach 50 first.

Sound easy? Players flick their shooter, but it can easily miss a marble entirely or strike the marble but without enough force to roll it outside the ring. If that happens, the player loses his turn, which can be deadly since, as in billiards, the very best competitors can easily go on long runs and win games without relinquishing a turn.

Yesterday, Nicholson, who had won the championship three times before, made it to the final match against Jeremy Hulse, 16, a high school junior from Hagerstown, Md. As their parents watched and paced nervously, Hulse went up first.

It was a seesaw match. At the end of the first rack, Hulse was winning 7 to 6. At the end of the third, Nicholson had mounted a comeback, and by the end of the fourth had a commanding lead, 32 to 20. But then, Hulse started chipping away fast. "I don't know how he gets backspin with sidespin," Nicholson said aloud from the sidelines.

"I know, it's insane," said Hulse's brother, Jonathan.

But it was too much for the high-schooler. Nicholson won 50 to 34 and took home the $500 check for first place. He beamed and pumped his fists in the air.

And how should an unemployed 20-year-old marbles champion spend all that cash?

His mother, Michelle, offered a suggestion: "Car insurance."

Robbie Nicholson blows on his "shooter," a ball about the size of a marble but made of glass or stone, before firing during the U.S. Marbles Championship.The grip is crucial in marbles, and its texture must not be disturbed or a player could lose his or her flick.Audience members watch as player Ralph Dillon, center, competes in a semifinal match. As in golf, spectators at marbles competitions speak to one another only in hushed tones.Robbie Nicholson shows his affection for the first-place trophy he won, along with a $500 check. It was the fourth championship for the Clarksburg, W.Va., 20-year-old.