When Bobby Clampett gives a golf clinic, you show up.

Some players can hit a golf ball high or low, fade it or draw it on command, and do it all while they're entangled in microphone wires and giving a technical lecture to a crowd of a thousand people.

Bobby Clampett can do all that, too.

But he does it on his knees.

One knee. Two knees. Right-handed. Left-handed.

Yes, addressing the ball left-handed on two knees with a right-hander's golf club turned upside down and backward, Clampett can drill a low hook that travels 200 yards and ends up in the fairway.

Sometimes.

"Hey, even the Harlem Globetrotters miss a shot from half-court every once in a while," said Clampett, when a delighted crowd at Congressional Country Club gave him an appreciative "booo" yesterday evening when his first attempt at this almost impossible shot squirted only a few silly yards.

Clampett, who just turned 23 and has already finished 14th and 17th on the money list the last two years, is a perfect example of the sort of gifted player with exuberant high spirits that the PGA Tour needs.

After his practice round yesterday for Thursday's opening of the $400,000 Kemper Open, Clampett went to the driving range to delight a grandstand full of aficionados. When golf loses its Walter Hagens and Jimmy Demarets, its Lee Trevinos and Chi Chi Rodriguezes to middle age, the sport always seems to have the good fortune to find a new face who knows how to make a too-grim game fun again. For the golf tour, Clampett on his knees is the answer to a prayer.

As Clampett and Scott Simpson, who has won more than $100,000 on tour for three years in a row, began their clinic, a voice from the crowd yelled, "Hit one from your knees, Bobby!"

"What do you think this is? The U.S. Open?" replied the laughing Clampett, who was pulled off the U.S. Open course in midround in 1979 when, performing as a noncompeting "marker," the then 19-year-old entertained the galleries with harmless trick shots--on the course.

The 5-foot-10, rail-thin Clampett took to his knees a half-dozen times yesterday and, on every occasion, blasted 240- to 250-yard drives perfectly on target; each time, he'd announce a different shot trajectory ("this will be a high draw"), then explain the swing theory involved in playing the shot and, finally, execute his own advice perfectly.

Asked how many players on tour could could hit Grade A drives from their knees, perfect iron shots from one knee, and left-handed trouble shots with upside down clubs, Simpson mused, "Oh, I'd say there's maybe . . . (dramatic pause to count) . . . one."

What makes Clampett so special--a player who is already observed, consulted and respected by his tour elders--is not some fluke capacity for trick shots.

Clampett says it best himself. "To me, golf is a science and an art and a sport. How many careers can you say that about?"

Few players are as severely analytical as Clampett, who is a natural student with an associate degree in French from Brigham Young University. He can talk into the night on the avant-garde theories of "the Golf Machine."

In fact, Clampett's amazing clinic shots are, in large part, a way of illustrating his theoretical notions on the game. As soon as he asked the crowd, "What is the source of power in the golf swing?" he heard the answer he knew would come: "The legs." Thus spake Jack Nicklaus for 20 years and thus the credulous public believes.

"Is that so?" said Clampett, falling to the ground to disprove the point.

In just 45 minutes, Clampett took the crowd from elementary pointers about balance, alignment and stance ("Imagine that you're balancing a glass of milk on the back of your neck as you swing") to discussions that were genuinely advanced.

Maybe the hackers in attendance won't be able to pass a quiz on the morrow, but they had a chance to understand why "the club shaft always points at the plane line, except when it's parallel to it."

For the 142-pound Clampett, who hits the ball a ton, the four sources of power are "the right arm going from the bent to the straight condition, the left wrist cocking and uncocking, how the left wrist rolls through impact and how the left arm comes up and away from the body on the follow-through."

Don't mention Clampett's notions about "learning to release the power accumulators" in the presence of the game's elder statesmen; it ain't exactly the same old stuff. But then neither is Clampett.

"Obviously, golf's a sport because you have the elements of competition, performing under pressure . . . having to adjust to circumstances. But it's also an art because, above all, you have to translate mechanics into feel. Even if you start with the science of the swing, you have to reach a point where you're playing with feel and instinct. It's a sort of sixth sense."

Clampett stops in the middle of the sixth fairway, about 80 yards from the flag. "If the ball is here, or here," he says, pointing to two spots only a yard apart, "I may play two entirely different shots. I can't completely explain why. You look at the lie, the tilt of the fairway and you imagine how the shots feel.

"If it were here, I'd play a draw in over that lake," he says of one spot. "If it were here, I'd play a high, cut fade," he says, pointing to an apparently identical spot a pace away.

"That's art."

Golf may be science and art and sport to Clampett, but it is also a mystery, just as it is to all golfers. Last season, he won a tour event and finished third in the U.S. Open; but he also had the British Open in his hip pocket--leading by five shots after two rounds--and blew sky high, finishing 10th.

As recently as last month, Clampett "threw every club in the bag" during an exasperating tournament in Texas. Now, however, he seems ready for business again. "He's ready to break loose," said his caddie. "No excuses this week."

Last year, on his first visit to Congressional, Clampett was tied for the first-round lead with 69, then had to withdraw because of a hand injury he incurred on the 11th hole. Even Clampett can't swing with one hand.

Now, he is back on the type of difficult, classic course that favors his exemplary long-iron game.

As he left his clinic yesterday, a little boy came up for an autograph with the top still screwed on his pen.

"Do it like this," said Clampett, getting the pen ready for action and showing the child how to hold his program out with a white space available for a visible signature. "It'll help, especially if you're trying to get Jack Nicklaus' autograph and there's a long line."

If golf is lucky, someday there'll be a long line behind Bobby Clampett.