CHICAGO (CBS) — Final preparations are underway for the NATO Summit this weekend, as downtown businesses and residential buildings begin taking extra precautions.

As CBS 2’s Susanna Song reports, workers are appearing all around the downtown area to secure buildings in case the worst happens. Around 4 a.m., a board-up company arrived at a condo building at Roosevelt Road and Wabash Avenue and began boarding up the windows.

This week, more and more residential and commercial building managers have been protecting their property by boarding up windows and front entrances. They say it is best to take action before protesters get out of hand.

The company, Buzy Bee Board-Up, says it has been particularly busy because of the NATO Summit. The company’s business has spiked 20 to 30 percent.

The apartment tower at 2210 S. Michigan Av. called Buzy Bee about a long stretch of ground floor glass windows on a building right in the protest zone.

The board-up met with approval from the building’s residents.

Tenant Bruce Walker said, “Wonderful, take care of it now, because we never know what’s going to happen.”

Fellow tenant Ruby Gray said, “A storm is about to hit, and you never know how bad it’s gonna be. So it’s always best to prepare.”

The glass entrance door to the building was covered, too, with a transparent sheet of bullet-proof plastic.

“They’ve got a tempered glass, which is a safety glass, in there right now. But any hammer, anything that you’d hit it with, it would crumble,” Buzy Bee president Steven Trzaskoski said.

Meanwhile, protesters have begun to flood into the city from out of town. A bus full of protesters from New York City arrived in the East Lakeview neighborhood Wednesday night.

Fellow protesters cheered “welcome to Chicago” as a charter bus carrying 45 protesters arrived at the Wellington Avenue United Church of Christ, 615 W. Wellington Ave., after a 38-hour ride from New York City. That church has offered to house as many protesters as it can hold during the summit.

A sign has been posted at the church reading, “Occupy Chicago Convergence Space.”

“I started off as an anti-war activist, so coming for NATO, you know, what’s a bigger anti-war thing to protest than NATO?” protester Michael Bellagatti told CBS 2’s Mike Parker.

Bellagatti said “99.9 percent” of his group is peaceful, but some of them may act “immature” or “sophomoric.”

Occupy Chicago says it plans to invite at least 1,000 more out-of-town protesters by bus before the end of the weekend, and at least a dozen more buses are expected to arrive on Thursday alone.

While the major protest groups have all ensured that peaceful and nonviolent demonstrations are their only interest, there are concerns about interference from other groups.

Headlines have appeared this week about protesters who might use “black bloc” tactics. “Black bloc” protesters dress all in black and often cover their faces, and have been blamed for destroying property and confronting police officers during demonstrations.

The Web site “Anarchist News’ indicates that some protesters had planned for black bloc tactics during the May Day march earlier this month, and that they were “tempted” to destroy property.

“We had no original intentions of destroying property on May Day. Despite the overwhelming temptation, we knew the state would be well prepared for it and our low numbers posed a safety hazard for handling them, doing anything and successfully vanishing in a crowd dominated by the monitoring peace police,” a statement on the site says. “Our original intent was a Black Bloc visual demonstration to bookmark Chicago for all to see while in solidarity with the workers as well as a symbolic preface for actions that lay ahead.”

The statement does not specifically reference the NATO Summit, but does invite anarchist protesters to “join us in the actions that lay ahead.”

“We invite everyone-including our ‘all seeing’ peace police friends-if you dare to dream bigger than the institutions and structures that obstruct our liberation,” the statement said.