The white frame barracks with green roofs, circa World War II and the tall shade trees around them give this wooded part of Fort Belvoir the sleepy look of a deserted summer camp before the kids arrive.

The barracks are long since outmoded and eventually will be razed. But in the meantime, the buildings that once housed men in uniform now are classrooms and workshops humming with activity.

This is the Fairfax County skills center where the county'a unemployed and unskilled can learn a trade - and get paid to learn it - under the federal Comprehensive Employment and Training Act (CETA).

Carpentry, air conditioning, building maintenance, electrical engineering, office skills and auto mechanics are covered in the all-day classes attended by a cross section of the unemployed-housewives returning to work. Southeast Asian refugees, single mothers, high school dropouts and welfare recipents among them.

Most of the center's seven instructors are rough-and-tumble tradesmen like carpentry instructor Robert Stets, who began teaching after a construction accident forced him to abandon his building business. The friends and contacts the instructors made in their trades are now employers of many of the persons who complete CETA training at Fort Belvoir.

"The ones who come just 'cause they have nothin' better to do, they don't stick around 'cause we cut 'em," Stets said. "The ones that wanna learn, well, I could get all my students here jobs this afternoon."

Usually the center trains 15 students in each class; the training last about six months. But some students have trained for only three months, while others have trained as long as nine months. Stets said he has placed about 80 percent of his students, and most started earning at least $4 an hour. Students are paid $2.30 an hour during training, although welfare recipients receive a smaller weekly stipend.

Two weeks ago, there were only four or five students in most of the classes because the annual $250,000 CETA budget for the skills center ran out and will not be replenished until October. Michael Gilbert, director of the Fairfax County Department of Manpower, said the shortfall is normal for this time of year. But some instructors at Fort Belvoir, who are paid $24,000 a year to teach there, were bemoaning the fact that they had so few students to teach.

Nevertheless, the four students Stets had in his class were busy putting finishing touches on a solid picnic table to be used on the base. And the sometimes-lavish interior of the barracks, occupied only by "two inches of pigeon leavings" when the skills center moved in, displays the work of more than 600 students who have filed through the classes since CETA training started in 1974.

Renovated air conditioners junked by the Army and repaired by students cool the buildings. Sophisticated lighting fixtures which can dim and throw a myriad of color, decorate some instructors' offices that were partitioned off by carpentry students. Skills center director Russell Crosier's office looks something like that of a bank president, and a renovation that Stets' students completed recently while Crosier was away at a conference.

Encased bookshelves, walnut wall panels surrounded by white plaster give it an elegant look, and a suspended ceiling made of what looks like soundproofing material gives it a modern touch.

"Russ wasn't mad when he got back," Stets recalled, chuckling. "But he never would have let us at it if he were here."

In one of the barracks, model homes are going up so carpentry students can practice building, plumbing students can practice putting in bathrooms, and electricity students can practice wiring.

About a mile away from the barracks in a wooded grove, another unused Army building serves as a garage for CETA trainees learning how to repair cars. The garage has the latest in car testing equipment, made available through a Ford Motors grant. For the cost of retail parts and a $2 labor fee, anybody can get a car repaired there, but mostly military families use the garage now.

"One MIA woman (a wife of a serviceman missing in action) brought her car here and the next thing I know I'm swamped with MIA women," said auto mechanics instructor William Jordan. "The word got around fast."

Linda Puryear, 26, is one of Stets' carpentry students who is trying construction work as an alternative to clerical work. Puryear, who is raising her two children alone, sees construction as a well-paying alternative to monthly welfare checks of $320 out of which comes $225 in rent and $40 for food stamps. "I want to be comfortable like anyone else," said Puryear, who lives near Baileys Crossroads. "But without skills, it's rough out there. Right now I'm pinching pennies, because I've got to have a car to work. I know, though, that this is a skill, and if I'm good enough, I'll get paid."

Stets says Puryear is good, and after a few more months in training is certain he can get her a "decent job."

Puryear doesn't assume she will be a successful carpenter. After stints as a day care aide, hospital worker and training for clerical work, she is not confident she will stick with construction.

"I just want to see if I can do it, and this (training) is half a chance to try."

Thirty percent of the students at Fort Belvoir are like Puryear, there because of CETA funds. Fifty percent are military, and others are sent through individual contracts under a sharing agreement among the Army, Fairfax County and Fairfax County Public Schools, which operates the skill center, Stets said.

Fairfax County CETA trainees also study at the Northern Virginia Skills Center in Arlington and at private companies. The Department of Manpower Services estimates that 60 percent of all trainees find jobs.

"I call this a good program because we train people for jobs that are out there," Stets said. "We have washouts, but mostly we have people who want to work and all they're looking for is a way to get to first base."