The five pickets wore work clothes and moved in a tired circle under a heavy gray sky outside the Scan furniture store in Greenbelt, observing Labor Day 1987 in their own fashion. Yesterday began their 19th week on the line with still no contract in sight.

"I'm at the stage now where I don't think we'll ever go back," said Mike Weems of Bowie, a $10-an-hour warehouseman with eight years on the job before Local 400 of the United Food and Commercial Workers union struck Scan furniture on May 2. "I had faith at first."

Yesterday, as America took a holiday to honor its work force and bid a relaxed farewell to summer vacation, the Scan strike remained one of several protracted walkouts in the D.C. area.

Labor Secretary William Brock marked the day with a generally optimistic note on NBC-TV's "Today" program, praising a new spirit of cooperation between industry and labor, while elsewhere the holiday took a traditional course: Tourists strolled the District, shopping and munching snacks, while labor leaders extolled the virtues of their movement and urged members to honor it.

"I don't know why labor shouldn't get together to remember the meaning of the day and restore the pride in being a union member," said Ernie Grecco, the new president of the Baltimore Metropolitan Council of the AFL-CIO.

The council sponsored a Labor Day Mass at the Basilica of the Assumption in Baltimore, with Archbishop William D. Borders as the celebrant and the Rev. Joseph Bonadio, whose father was a national leader of the Sheet Metal Workers International Association, blessing the tools of the represented trade and craft unions.

In Virginia, David Laws, president of the state AFL-CIO council, said that Virginia unions have not been battered as hard as those elsewhere.

"We've been holding our own," he said. "Some states have been devastated by plant closings and industries going overseas."

In the District, meanwhile, Larry and Mary Curtis of Louisville took in sights and bade goodbye not just to summer vacation but to their 16-year-old son Mike, who will stay behind to work as a House page.

"This is the last thing we're doing in D.C. before we head back," Mary Curtis said, gazing up at the Jefferson Memorial.

"We hit the Smithsonian, but not as much as we'd like to," her husband added. "But our younger son has already started school, so he's at home with friends. We've got to get back and head into fall."

Bruce and Julie Isett of Joppatown, Md., treated their 6-year-old daughter Julie to her first look at Washington, although Bruce Isett had more on his mind than sightseeing.

"I've got to drive back up I-95 this afternoon," he said with a grimace.

As tourists took yesterday in easy stride, Grecco called for a labor union parade in Baltimore next year and Brock told the "Today" audience: "I think American business and labor are leading the way and showing other countries that we can create more jobs by cooperation . . . . "

That spirit of cooperation is much stronger today than it was even a few years ago, Brock said. "That's very healthy."

Weems and fellow strikers outside Scan furniture's Greenbelt store took a different view.

Despite Brock's upbeat remarks, America's labor movement appears confronted by its most serious postwar challenge, with more-militant management taking an increasingly harder line against fragmenting unions. Weems, 38, stood in the Greenway Center shopping plaza yesterday, wiped sweat from his forehead and gave voice to his opinion of that changing relationship.

"I'm just hoping we can take the company down with us," he said, and those around him nodded. "I'm out here to keep people out of the store, to keep money out of the store, to take them down."

In all, 170 sales, delivery and warehouse employes have been picketing Scan's 11 stores in metropolitan Washington and its administrative offices in Savage, according to Thomas McNutt, president of the 47,000-member local. He has accused Greenbelt Cooperative Inc., which controls the stores, of trying to squeeze out the union.

Greenbelt, a 45-year-old consumer-owned enterprise, has denied the charge. The company has replaced strikers with nonunion workers and the two sides have not bargained since the strike began, McNutt said.

"It gets kind of discouraging out here," said Lou Wan, 27, a warehouseman who earned $11 a hour before the walkout. The union pays him and other strikers $4 for each hour they spend on picket lines. "I've always heard about unions and what they can do for people . . . . But now everybody's at a standstill, and I don't know what to think."

Weems said he has received mail from the cooperative urging him to abandon the local and return to work at his old wage.

At first, he said, he gave the offer no thought. "Yeah, then these last few months the bills have been piling up. These last few weeks, I've been tempted . . . . "

For now, though, he walks.

Staff writer Kent Jenkins Jr. contributed to this report.