"IT REALLY gets me, all these kids who expect to go into commercial art and they take a liberal fine arts course and do abstractions and things. They can't draw a chair."

Sometimes Sandra Correnti takes time out from her frantic schedule as an independent advertising artist and lectures at area high schools. Students show her their portfolios, and she tells them what her world is really like.

"It's a 14-hour day," she says. "I have my studio right off the bedroom. I get up at 3 a.m. sometimes. There's always those deadline jobs when they have to have it yesterday and the Federal Express truck is sitting in the driveway with the engine running. My whole life is a deadline."

You get paid by the hour, and you draw what you have to draw: furniture, housewares, shoes, cameras, karate fighters, office equipment, trucks, silver teasets, toilet seats. . .

"I've drawn just about everything there is to draw," she says. "Mattresses are the worst, the bane of my existence. I must have drawn 125 mattresses."

It has to be fast and accurate. No distortions. She works from photographs or from the item itself. "When they send me a load of silverware or kitchen gadgets or dishes or something, the stuff is all over the house and it looks like I'm a fencing operation."

Some of Correnti's work is astonishing. Her 1975 line drawing of an Oriental rug is still used in W & J Sloane newspaper ads. It is a gorgeously detailed picture of an elaborate rug that took her 2 1/2 days. She worked full time for Sloane then. Later it was Hecht's, where she drew furniture so well that people bought the pieces just from the ad, over the phone.

Today she free-lances for numerous retailing chains -- in New Jersey and Cleveland, Colby's in Chicago, Barker Bros. in Los Angeles and several Washington department stores. Her husband John, whom she met when the two upstate New Yorkers were students at the Art Institute of Pittsburgh, is art director and graphics manager for an industrial firm. They live in a sprawling, immaculate ranch house and farm near Leesburg, complete with just-baked apple pies in the pantry.

"I always wanted to be an artist," she says. "I think of myself as a portrait painter, but I just don't have the time. I keep thinking when the kids are gone I'll take it up."

The kids are the three teen-agers she has been raising all the time she has been working her 14-hour days. Once in a while she will sketch a profile at the kitchen table ("David, just keep talking the way you were. . ."), and now and then she rips off a quick portrait "to see if I've still got it." Hanging on her studio wall is a casually flawless pencil sketch of a young girl. "It scares me: The eyes follow you around the room. Spooked by my own drawing!" She laughs. She drew it in an hour.

"There's such a crying need for furniture artists," she says. But many can't do human figures, which often are needed to put a little excitement into, say, a picture of a carpet. So Correnti is in constant demand. She can knock out three ads a day, including perhaps three bedroom suites, a dining room and five sofas with print fabric, all done in precise pen crosshatching with a bit of wash for shading.

"I started when the children were small, working in the house. I didn't even have a drawing board."

Some days, she admits, it's all she can do to face the board, and she thinks she's lost the touch. But then the phone rings.

"I never know when work is coming. There's a certain insanity to it," she says cheerfully.