Many city businesses share a quandary with antiques dealer Karl Kemp: homeless people setting up camp in front of their shops. While Mr. Kemp tackled the problem by filing a $1 million lawsuit against four people who frequented a heating source in front of his Madison Avenue store, others have taken different approaches.

At a bar and restaurant at the bustling intersection of Bleecker and Crosby streets, the Noho Star, a two-foot-long vent emits heat onto the sidewalk from the prep kitchen in the basement, and homeless people have spent the winter hovering there for warmth. In response to the unwanted spectacle, the management of the restaurant had a metal barrier constructed over the vent. Functioning like a barbed wire fence, the makeshift shield has metal spikes that discourage loiterers from lying on top.

The “grate” is the latest effort by managers to deter homeless people. On several occasions, they have called the police and homeless organizations to find a new spot for the homeless men who sit in direct view of restaurant patrons. Even when the loiterers are picked up, though, they return within a day.

“When they come back, you just feel kind of defeated,” a Noho Star manager, Julia Lisowski, said. She laughed when asked if the restaurant has any plans to sue.

Two homeless men, Rudy Astore and Curtis Cooke, can usually be found at the M&N Superette on the Upper East Side sweeping the sidewalk in front of the flower stand or panhandling for change. Mr. Astore has made the area in front of the grocery store his home for the past 20 years, while Mr. Cooke arrived five years ago.

Rather than constantly spar with the men, the owner of the supermarket, Dong Koo Lee, has put them to work.

“They’re poor guys, I can’t kick them out,” he said.

Instead, the two help out around the store by cleaning the sidewalk, watching the flower stand at night, and keeping an eye on delivery trucks so they don’t get ticketed.

This reciprocal relationship goes on to the chagrin of many neighbors, who don’t appreciate the constant panhandling by the men, Mr. Lee said.

City residents bothered by homeless people in their neighborhoods are left with few options. Even though outreach workers are trained to motivate people to get off the streets, a homeless person can’t be unwillingly taken to a shelter, the executive director of the Neighborhood Coalition for Shelter on the Upper East Side, Anne Teicher, said.