Her hair dryer, Elizabeth Elsberg complained, was too hot to handle.

Sidney Katz gave his diagnosis: a maladjusted thermostat. With that, Elsberg bent over the workbench and went to work on the disassembled appliance with a pocketknife, gently prodding the tiny sliver of metal Katz had pointed out.

When she put the 1,600-watt hair dryer back together, it blew cold air. But Katz was pleased. "You can see we're working with the right part," he said. Sure enough, with a few more adjustments, the hair dryer was fixed -- another successful repair job for Katz's "Fix-It-Up" course in home maintenance and repair.

For his students, who meet two evenings a week at T.C. Williams High School in Alexandria, the mended hair dryer was also another victory in the homeowner's relentless battle with broken appliances, leaky faucets, wilted air-conditioners and hundreds of other minor breakdowns that rob them of convenience, time and money.

Katz, who has taught the adult education course for nine years, caters to those who consider themselves tool-illiterate and mending-impaired; those who feel the closest they can ever come to being "handy" is to mumble darkly about "gremlins" and reach for the Yellow Pages to call a plumber or electrician.

"What's the difference between someone like myself who can fix most anything and someone who can't fix anything?" asks the 54-year-old Katz, who exudes enthusiasm for the inner workings of things. "It's just knowledge of how something works. I train people in what I call the 'theory of repair.' I teach them what makes things work.

"People say, 'I don't know how to repair anything' or 'My wife sent me here.' But when they get out of the course, they can repair anything."

Well, almost anything. "We can't fix a cat or a dog," he concedes.

His curriculum includes lessons in fixing toasters, irons, clocks, faucets, light switches and vacuum cleaners. He also teaches minor repairs on cars, furniture and bicycles. A graduate of his eight-month course also learns to solder, plaster, wallpaper and replace window panes, often by doing these jobs as a class project in one of the students' homes.

Students also bring their broken appliances to class. "Ninety-five percent get repaired," Katz said. He added that he does not bring his tools to class. "The students do the work."

"Some people take the course two and three times; it's doing the work that helps you learn," he said.

Katz, who grew up in Northeast Washington and owns two car radio stores in Northern Virginia, is mostly a self-taught handyman.

"My first job when I was a kid was to go into a notions store where they had cars and wagons," he said. "I would put them together and the man would pay me in school supplies . . . . I just seemed to be mechanically inclined when I was young."

A staff member at T.C. Williams, where he sometimes is addressed as "Mr. Fix-It," Katz seems to have "a vast array of a broken something-or-other," said one of his students, Bruce Schmid.

One of Katz's best classes, Elsberg said, is in tools -- how to use them, which are good ones and which are useless. "It makes people brave about using tools," she said.

"I think it's a great course," said Alexandria physician Hernando Salcedo, who took Katz's course last year because "I was tired of getting people to repair everything in the house. It should be a must for everyone who owns a house."

In one recent class, which met in the mechanical drawing room of the high school's adult education center, Maria Moore dumped two long strands of outdoor Christmas lights on the workbench.

"I just picked them up at a yard sale for $2," Moore said. "I thought I'd check them out . . . . I brought my soldering iron along."

"Something like this would be unsafe to use," Katz said, pointing to a mess of melted green plastic around one of the plugs. "It got hot and shorted out." The students cleaned the plug, did some rewiring and tested the lights, now ready for this holiday season.

"It pays to repair something like this," said Katz, noting that new ones do not come cheap.

"Now we know why they were in the yard sale," quipped Schmid.

"Somebody didn't know how to fix them," Elsberg added, a touch of triumph in her voice.

A trip to the bathroom was next on the agenda. "We're going down to the teachers' lounge to fix a spigot there," Katz said. "Bring your tools along.

"Turning off the water is a very important thing . . . . If you don't turn it off, you only do it one time and you remember it the rest of your life."

Student Gene Dawson did the honors, unscrewing the faucets and extracting the washers, which Katz held up to show where they were worn and torn. "It's fast if you know how," he said. "Quicker than you can call a plumber to come, you can do it yourself."

And that's the added attraction of his course, Katz said. "You save a lot of money, a lot . . . . Doing one repair yourself, you can actually pay for the course." (Students pay $57 for four months and $108 for the full eight-month course.)

Said Moore: "I've learned a lot from this class. I've fixed the latches on the windows at my beach home and I fixed a leaky trap in my sink.

"Now I've got to learn to fix my furnace."