Beatrice West, a housewife, heard something in her Southwest Baltimore neighborhood that sounded too good to be true: the federal government had 70 job openings for unskilled workers. She rushed to tell her daughter, who told a friend, Wayne Fields.

Fields jumped in his car yesterday and headed downtown to apply. On the way , he saw his bother and a friend, both of the jobless hanging out on a corner. He told them. They decided to come along.

About 15,000 people had the same idea. Almost all of them are black, most are unemployed, many are on welfare. All day yesterday and early today, they lined up for blocks and waited for hours to pick up applications for the 70 clerical and manual jobs coming open in January at the Social Security Administration here.

Local officials and welfare rights leaders called it an "astounding" and "unprecedented" demonstration of the severity of unemployment here, particularly at the lowest level of the economic ladder.

About 40,500 people in Baltimore are unemployed, according to the Department of Labor. That represents 9.9 percent of the work force, 2 percent above the national unemployment rate. The jobs being offered here are at the lowest level of the federal pay sscale, paying from $7,210 to $11,555 per year. They are classified as worker trainee jobs, meaning that those who are hired will not become permanent federal employes in less than three years.

Despite the low pay and the potential job security problem many Baltimoreans standing in the lines to apply for the jobs said they knew of no better opportunities.

Serena White, 45, an unemployed mother of two who is now on welfare, took a bus downtown and hobbled on a crutch for two blocks between the bus stop and the Garmatz Federal Office Building, one of the job application sites.

She was injured in a bus accident, she explained, pointing to broken toes on both feet and her mouth, which was missing several teeth.

"Whatever job there would be I would take," she said. "They say there are jobs in this city. I've called all the want ads. I've visited all the offices. There aren't even jobs that I don't want, much less jobs that I want.

"I might as well become a criminal. They do more for convicts and ex-convicts than they do for the people who are trying to walk a halfway straight line."

Social Security officials said they intentionally avoided publicizing the openings except to notify the state unemployment office and the federal jobs information center. "We knew we'd get a lot more people than we had hoped to use. You always do with entry-level jobs," one official said.

The speed with which the information spread, mainly by word of mouth, shows the desperation of Baltimore's poor to enter the work force, said Robert Cheeks, executive director of the city's Welfare Rights Organization.

Ministers announced the openings in church services over the weekend, and current Social Security Administration employes told their neighbors and friends. Serena White said she read about the openings in a Democratic women's culb flyer.

"Everyone seems to be trying to do something to help people get jobs, but what it does is heighten the frustration," Cheek said. "Every time one person hears about a job, 25 or 50 people hear about it."

Cheek said his own organization recently had 1,100 applicants for 400 jobs in a work incentive program, "and that was before we could even advertise."

Wayne Fields said he could have picked up "a busload" of jobless people to bring to the application site yesterday instead of bringing only his brother and a friend. They call their southwest Baltimore neighborhood "The Valley," because so many people are out of work. He and his brother, Marvin, 20, and their friend Wayne Webster, 21, said they were discouraged to find that so many others had applied for the jobs.

"It's just danged hard," Wayne Fields said. Marvin Fields and Webster chimed in a sort of chorus: "This place is tight," Marvin added. "There's no opportunity," said Webster.

Social Security officials said it will take three months to process the applications. They said they expect to fill 68 to 75 jobs in the Baltimore Social Security offices, and place the names of all other eligible applicants on federal job registers.

The lines at the Garmatz building Monday were the longest that formed at any of the three application sites. An estimated 5,500 people picked up applications Monday at the federal building, which stands about a block from Baltimore's glistening new harbor front developments. Cheeks called the juxtaposition of the nationally renowned harbor and the job application lines ironic.

Marvin Fields put it this way: "They's putting up warehouses and buildings and all kinds of stuff, but there still ain't no work."