An island of artificial green grass, pocked with holes, quilled with pins, and shaped like a kidney, lies in the middle of a concrete patio on top of a new three-story garage at Chevy Chase Chevrolet in downtown Bethesda.

This unlikely sight is, of all things, a putting green -- a token of country club life that is Fred Bowis' way of satisfying a Montgomery County zoning ordinance that requires some new buildings to offer "amenity space" for the well-being of this ever-conscientious county's residents.

"What else would you do?" says Bowis, president of Chevy Chase Chevrolet, stroking a putt past the third hole of the green on the roof of his dealership at 7725 Wisconsin Ave. "The space wasn't large enough for a tennis court. I just upped and said, 'A putting green!' and an architect said, 'What a great idea!' Number 3 breaks to the right. It's harder than it looks."

When Bowis, a trim 41-year-old who now keeps a case of golf balls and two putters in his office so he can practice his stroke, wanted to add a storage garage and service area to his dealership two years ago, he had to file a prject plan with the Maryland-National Capital Park & Planning Commission. Because his business was located in an area known as the Bethesda Central Business District, and because he chose to cover all of the land he could with his new building, the zoning laws on the books since 1974 required him to dedicate 20 percent of his planned expansion to "amenity space."

Amenity space typically means droopy shrubs and woodchips strewn about in a garden tableau, or walkways and fountains in a plaza. Such "amenities" are provided by the developer in exchange for the planning commission's allowing a more complete use of the scarce land in the highly developed central business district.

After figuring out the formula, Bowis and his architect found that they would have to put more than 3,000 feet into amenity space, and that it had to be available to the public during the dealership's business hours. They potted some plants and sprinkled some woodchips on the street level but there wasn't enough room at street level to satisfy the zoning requirements. So they designated space three stories up in the air over the garage where new Chevys were stored.

And when it came time to decide what to do with the 50-60-foot concrete patio, Bowis, who has a 26 golf handicap but describes himself as a "good putter," had the idea for the putting green.

"That's part of its charm," Bowis said. "The Jewish people have a word for it. It's called chutzpah. When we were designing the green the architect only put in 8 holes. I said, 'If you're going to do it, you got to go all the way.'"

Such vision, however, is not cheap. According to Bowis, the total cost of his new concrete and Astroturf complex was $100,000. It opened in mid-August, but so far the putters are as scarce as holes-in-one, amounting to one or two a week, not including the half-dozen employes at the dealership who bring putters to work, and eat lunch at a greenside in the "gazebo" with its view of beautiful downtown Bethesda.

"The novelty of it will attract business," Bowis insists, although he says he doesn't care to see gangs of club-wielding teen-agers monopolizing the course, so he has decided not to supply putters or balls, except to prosepective customers.

One of the first putters was 72-year-old Leo Pallin, who has designed a putter Bowis calls "the ideal instrument to propel a golf ball."

"I think the green is a helluva smart idea," Pallin said. "Sometimes if you're getting your car repaired you have to wait around forever while they fill out papers. It can't duplicate a real grass green, but as far as artificial surfaces go, this one looks pretty good. It was working for me. From three feet I can make a putt with my eyes closed -- literally."