LOS ANGELES — Shortly after his release from prison four years ago, Julio Silva entered the apprenticeship program in the Ironworkers Union Local 433 in La Palma.

To his alarm, he learned that ironworkers called all first-year apprentices "punk."

He had been an East Los Angeles gang member, a drug user and a car burglar in and out of jail. In that world, a "punk" was someone's prison sex slave.

But Silva tried not to let it bother him. The more he worked at his new job, the more his skills improved. Ironwork became the one legal thing he had done well. It also paid $29 an hour, plus benefits.

Glimpsing a future, Silva's desire to do drugs was replaced by his determination to master the use of sleever bars and spud crescents.

After Silva's first year on the job, the ironworkers simply called him Julio.

"I never thought my history would allow me to have something more than $7 an hour," said Silva, 37. "I don't see this happening nowhere else but in the union. It's given me the best opportunity of my life."

Silva is among a growing number of Southern California gang members who have joined building-trade unions over the past decade as construction work has boomed. These good-paying jobs were once reserved for those with family connections, as fathers recruited sons.

But today, beset by nonunion competition and an aging membership, unions have stepped up recruitment in minority enclaves where many young men have criminal pasts. Now homeboy recruits homeboy.

"We probably make up the majority of the workforce now," said Albert Frey, once a Crip and crack dealer, now an apprentice with the Steam-Refrigeration-Air Conditioning-Pipe-fitters Union Local 250.

No one knows exactly how many gang members are in the building trades because the unions have stopped asking about recruits' backgrounds. Some unions even will allow a man to remain a member while in prison — as Frey did for two years — if he pays his monthly dues.

"This is our gang now," Frey said, "in a positive way, though." For decades, membership in the building trades was tightly restricted. Unions controlled most of the work sites throughout Southern California and kept their numbers low.

"You damn near had to be a relative of somebody's," said Jim Watkins, business manager of the Heat and Frost Insulators Local 5 in Azusa, who joined in the 1950s. "It was tight-knit, almost like a lodge."

But by the 1980s, many contractors were bridling at union control. Nonunion contractors had emerged to compete for jobs. Among their employees were inner-city youths and ever-greater numbers of illegal immigrants.

By the early 1990s, veteran union members were retiring and membership fell, while work and nonunion contractors flourished.

"When we controlled 80 percent of the work, we were very cocky," Watkins said. "When we went down to 20 percent, we started re-evaluating."

A new generation of union leaders opened membership to almost anyone who wanted to work hard. They began recruiting aggressively in the inner city. Some stopped requiring a high school diploma or even that apprentices speak English.

Among those who responded were men with gang and criminal records and few options.

"These are the people who are undermining (unions) by going to work for nonunion contractors at much lower wages, with no benefits," said Sharon Delugach, staff director of the UCLA Downtown Labor Center. "Nobody likes change and these (union) guys like change less than anyone, but it's in their self-interest" to recruit in inner-city neighborhoods.

But there are problems with the more open approach. Since Sept. 11, many sensitive work sites — including government buildings, shipyards, chemical and nuclear plants, police departments and schools — require extensive background checks of workers. Those checks screen specifically for illegal immigrants and ex-convicts.

Not all gang members thrive in unions. Some take orders poorly, chafe at getting up at 4:30 a.m. and are happier selling drugs.

"It's hard for you to rip yourself away from it," said Armando Valadez, 33, who spent his first three years as an apprentice heat-and-frost insulator. "Every Friday (after work) I'd go and see some of my homies. I had a son, a wife and a union job. Still the gang was stronger."

Frey, the former Crip, was facing a drug possession charge when he joined the Steamfitters. He was convicted about a year into his apprenticeship program and sentenced to two years in prison.

He spoke with union officials, who gave him a leave of absence.

In prison, "I had time to sit down and say, 'Where are your priorities, Albert?' " said Frey, 40, married with three children. "You're getting too old."

Since his release last year, Frey said, he has left his gang activities and drug dealing behind and is now determined to finish his apprenticeship.

For those with prison records, he said, the building trades "are the only places that accept us."

Silva is in the last six months of his four-year apprenticeship. As a journeyman, his wages and benefits eventually will reach $49 an hour.

"My eyes get a little watery, where I was a few years ago and where I'm at now," he said. "It's like another opportunity of life. I'm proud to be an ironworker."

Union leaders say most gang members leave their affiliations at home and that work sites are remarkably free of street rivalries. The Ironworkers Union, in particular, has gone after gang members and parolees for work that is hard and often dangerous, laboring on bridges and soaring office towers.

"They take that street toughness that puts them into Corcoran or Pelican Bay (state prisons) and put it into this," said Robbie Hunter, president of the Ironworkers Union. "The electricians require algebra and all that. What we require is no fear. They're perfect for us."