In the chilly stillness of 4 a.m., Gavin Robinson and several other homeless men waited yesterday in a District shelter lobby for an old school bus to take them to eight hours of construction work that would put up to $30 in their pockets and a day's worth of dignity into their broken lives.

Robinson, 34, a Vietnam veteran who once owned a house, has been homeless for nearly two years. He hopes the day labor and another part-time job installing boilers will buy a one-way ticket out of the downtown shelter. After a number of setbacks, he has saved $495. Like many of the city's working homeless people, Robinson makes no predictions about when he will leave the shelter.

"A shelter is only a shelter and not home," said another man who lives in a shelter and also works. "You go because you have to preserve your dignity and buy a meal or buy your cigarettes and your shaving cream."

Contrary to the perception that homeless people are totally dependent on charity, a majority of the homeless men in District shelters work, according to the D.C. Department of Human Services. Experts suggest that many working homeless people have turned to shelters for housing of last resort in a city short of affordable alternatives -- and then find themselves trapped there.

"The District may be on the cutting edge of a new phenomenon: shelters serving as public housing for single men who work and don't earn enough to afford a place of their own," said Kim Hopper, an assistant professor at the City University of New York who has done extensive research on homelessness.

The D.C. Department of Human Services reports that 60 to 65 percent of the homeless men in city-funded shelters work full or part time. For homeless families the percentage is lower: Of 500 homeless families in the District, 15 percent receive their income solely from employment and another 7 percent receive a part of their income from jobs.

Employment figures were unavailable for single homeless women and District statistics did not indicate how many of the single men hold full-time jobs. Last year, a U.S. Conference of Mayors survey of homelessness in 25 cities found that an average of 19 percent of all homeless people in shelters worked.

The city's largest single group of working homeless people live at the men's shelter operated by the Community for Creative Non-Violence at 425 Second St. NW. Of the shelter's population of 575, at least 250 men held jobs this week, said Laurence Lyles, supervisor of the second floor where working men live.

One of the men, a 31-year-old man called "Curly" said he and his wife, a teacher, once made a combined salary of $30,000. When they separated, he said he did not have sufficient money to rent an apartment and believed that family and friends were too crowded to accommodate him. Now he makes $8 an hour on a construction job and visits his wife and three children on weekends. He has not told his family where he is living.

His situation, like that of other working men in District shelters, suggests that shelters are a part of a survival network for low-income workers who may not have sufficient skills or education to obtain higher paying jobs, Hopper said.

"For a lot of men, the shelters become part of a pattern of a makeshift existence which includes help from their families and friends and part-time work," Hopper noted.

Groups of homeless single men, women and heads of homeless families living in emergency shelters scattered throughout the District work daily as construction workers, hotel maids, receptionists and store clerks.

The majority of homeless workers interviewed asked not to be identified because they did not want to jeopardize their ability to mingle in the work world and on the streets without being identified as homeless.

On a recent evening, Eric, who became homeless in August and lives at a men's shelter on Irving Street NW, was dressed like a college student -- neatly creased jeans, Redskins shirt worn over a white shirt, wing tip shoes -- as he talked about spending a night huddled against a building after a labor pool van inadvertently left him at a Virginia construction site.

Another man at the Irving Street shelter who said he is a floral designer with steady employment for the last 17 years, has become skillful at hiding his secret.

To avoid giving his address to coworkers who wanted to send him Christmas cards, he lied and said he does not celebrate the holiday. When his mother came to town on a bus trip from Atlanta, he took her on a tour of the city and deflected her requests to visit his home. "It would kill her to know," he said.

But Delma Heron, a homeless man who works as a recruitment supervisor for Jefferson Business College in downtown Washington, is not secretive about his situation, and said he hopes his comeback will one day inspire others. Heron, who became homeless about three months ago after he got involved in drugs, lives at the CCNV men's shelter.

Yesterday, clad in a blue pinstripe suit, Heron delivered a lecture to the business school's recruiters. When one recruiter suggested that a salary increase would be the quickest way to motivate the group, Heron sternly disagreed.

"If you want it, you are going to have to earn it," he said. "You get nothing free in America."

As workers such as Heron struggle to escape shelters, the number of working homeless people around the country appears to be on the rise. A survey of 25 cities released last month by the National Coalition for the Homeless found that in 10 cities, shelter workers reported an increase in the number of working homeless who did not earn enough to pay for housing. The survey found that on average 30 percent of shelter occupants were working full or part time.

Anita Beatty, spokeswoman for the Atlanta Task Force on the Homeless, said her group found that about 40 percent of the homeless people in Atlanta shelters work. "We expect the working homeless to grow because the affordable housing stock continues to shrink." she said.

In the District, the city's departments of human services and employment services plan to increase their efforts to help the homeless find jobs. This year, the two agencies helped 150 adults who head homeless families living in city shelters.

Bob Taylor, acting chief of employment and training at the Capital City Inn, a hotel used as a shelter for 197 families, said he emphasizes finding full-time jobs that pay above minimum wage -- $3.35 an hour in the District.

"Some folks come back even if they leave with jobs," said Taylor. "We try not to get them jobs paying minimum wage because these folks have to support families, and we don't want them back in the system."