Unloved and janky, scaffolding is New York City’s other architecture, its Tinker Toy exoskeleton. It has enraged and inspired its residents, while forever altering their behavior — there are those who cleave to its shelter during bad weather, or skittishly avoid it — as they continue to rail against its persistence and ubiquity, perhaps unaware of the history behind much of it.

On a late May evening in 1979, Grace Gold, then a 17-year-old freshman at Barnard College, was walking with a friend on 115th Street when a chunk of masonry fell from the lintel of a Columbia University building and killed her. The next year, New York City adopted a law that required building facades be inspected regularly; under the law’s current incarnation, buildings over six stories must be looked over every five years. If they fail inspection, which they invariably do, aging masonry being what it is, building owners must install a sidewalk shed — what many call sidewalk scaffolding — to protect pedestrians while owners do whatever is necessary to fix the problems.

It was a good law, and it made sense to shield the public from projectiles hurtling from the sky, but many building owners opted to simply tack on a shed rather than do the more expensive facade work. Four decades later, Ms. Gold’s legacy — Local Law 11, or “The Facade Inspection and Safety Program” — accounts for about half of the city’s sidewalk scaffolding, with over 3,000 sites and nearly 900,000 feet of sheds.

The system sometimes works. Not always. One morning the week before Christmas, Erica L. Tishman, a 60-year-old architect and mother of three, was walking on Seventh Avenue near 49th Street when debris fell from a 17-story building and killed her. The building had been fined in April for having an unsafe facade, and again in July, while its owners challenged the city in court. On that morning in December, they had yet to put up a sidewalk shed.

An investigation by the city began; a sweep of the 1331 additional facades cited for repairs was made a few days after the accident. And the city has dramatically revised its policies. New measures include more frequent inspections, and if repairs aren’t made, city contractors will do them and charge building owners. In addition, the city will compel bad actors to get their sheds up and down in a timely and safe manner, through stricter fines that will be ten times what they have been in the past.

The average time for having a shed in place is about a year, but there are sheds that have been up for as many as 11 years, including at the Department of Buildings’ lovely landmarked headquarters on lower Broadway, once the site of New York’s first department store, opened in 1846. “Happy Holidays NYC,” proclaimed the building department’s twitter account announcing the shed’s removal last month.

But Local Law 11 is not the only driver of sidewalk sheds. The rest surround construction sites, and, taken together with those protecting facades, the whole adds up to more than 300 miles of scaffolding, much of it in Manhattan. If you think New York City is blanketed in the stuff, you are correct: just look at the Department of Building’s interactive map, with each sidewalk shed represented by a blue blob.

The city is lousy with them. And life adapts under the ongoing scaffolding occupation in curious and sometimes delightful ways.

The City’s Biggest Canvas

This past summer in Dumbo, the architect-developers of 168 Plymouth, an elegant conversion of two historic buildings, used their sidewalk shed as a planter, laying in native trees and vines that by fall had tumbled over the plywood and down to the street in a riot of umber and orange tendrils. When the work is done, the developers, whose company is called Alloy, plan to move the plants to an interior courtyard and a roof terrace.

“Dumbo is going through a lot of construction in a way that it hasn’t really seen before,” said Jared Della Valle, Alloy’s co-founder, “and we wanted to be thoughtful about something that’s never that fun. One of the things that’s surprising is how well the plants have thrived. If you thought about it on a grander scale it could be a pretty important part of our lives.”

In 2015, Zaha Hadid designed her own shed for her space-age building on the High Line, sheathing its innards, Christo-like, in whorls of silver and white fabric and topping it with a black roof. (“Allonge,” is what she called her “sculptural installation,” avoiding any reference to the lowly scaffolding shed.)

Over the years, the city has tried to ameliorate the look and feel of what many describe as an urban scourge. Last year, a public art initiative invited cultural institutions to treat the plywood sheds as canvas; as a result, the Studio Museum in Harlem, now in the first stage of building itself a new home, will use its sheds for art. In August, ArtBridge, a nonprofit that marries emerging artists to urban spaces, installed work on four sites.

Nearly a decade ago, the city held a competition to completely rethink the much-maligned structures. The winning design, from Young-Hwan Choi, then an architecture student at the University of Pennsylvania, in collaboration with Agencie, a Manhattan architecture and engineering firm, was a delicate white carapace with gothic arches and LED lights called Urban Umbrella. But it leaked rain on then Mayor Michael Bloomberg during a photo op, and for a long time proved too expensive to develop and deploy in this country. So Agencie took it to Canada and tested it there.

That’s when Urban Umbrella’s designers met Benjamin Krall, a 31-year-old venture capitalist interested in smart city innovations, as he put it the other day. “I got really interested in the scaffolding space,” he said, and dove in. Because Urban Umbrella is four times the cost of normal scaffolding, at first they gave it away for free. This year, Mr. Krall has 50 paying customers, and you can see Urban Umbrellas at 37 sites throughout the city, including the Ralph Lauren flagship on Madison Avenue, and the Yale Club on Vanderbilt Avenue. He hopes to “dominate in New York,” and also expand into other cities. “We closed a $3 million round of funding this month,” he said. “We’ve made scaffolding into a sexy asset class.”

Karrie Jacobs, an architecture critic, was surprised to find herself charmed. “In general when something mundane and ordinary gets redesigned to be stylish, I hate it,” she said. “But in this case I think it’s great because sidewalk sheds stink. So what if the Urban Umbrellas are a little bit froufrou? ”

Some members of the Yale Club, said Kevin Lichten, the architect who is chair of the Club’s house committee, are so pleased with Urban Umbrella’s lacy armature they are asking that it be permanent. “The whole arrival sequence into the club is very important,” Mr. Lichten said. “The brides for their wedding, taking grandma to her 90th birthday party. We knew it had to look good.” The arches remind him of the Rue de Rivoli, the Parisian row of shops from the mid-1800s. “And it really does protect you from the rain which is what everyone in New York wants.”

More grimly, they do the job they were designed for. Mr. Krall said he was sick at heart at the news of Ms. Tishman’s death. “Scaffolding is an unfortunate, necessary evil,” he said. “It would have saved this woman’s life.”

Who Lives Here?

Recently I tagged along with Max Wycisk, the 26-year-old operations analyst for the 34th Street Partnership, which oversees 24 square blocks in Midtown and Chelsea, a quarter of which is covered in sidewalk sheds. Each month, it is Mr. Wycisk’s job to organize their inspection.

He or a colleague will set out to measure the scaffolding (are there more or less linear feet, for example) and make sure that the sheds are lit properly and well-maintained. On that frigid night, he wore long underwear, jeans, a fleece vest and jacket and a watch cap as he made his rounds, nodding to the homeless across from The New Yorker Hotel on 8th Avenue, skirting puddles, trash and traffic. It took three hours — it is his habit to listen to sports podcasts as he works — but he found nothing awry, except the happy fact that more than 1,000 feet of sheds had been taken down.

Sidewalk sheds are shelter for construction workers during smoke breaks, and a destination for dog walkers during inclement weather. They are a little bit of home for the homeless; a young man in my neighborhood keeps vandals away with sign on his bedding that proclaims, “Bed bug infestation, do not touch!”

Bats sometimes roost in sidewalk sheds, as one did a few years ago on scaffolding overlooking the High Line. “It hung out there for a couple of days and moved on,” said Kaitlyn Parkins, an ecologist and bat expert. Rats, as it happens, are not shed dwellers, at least not typically, according to Matthew Combs, Ms. Parkins’ fiancé, whose Ph.D. examined how populations of urban brown rats are related to each other and tracked their movements through the city (yes, there are uptown and downtown rats). Rats need regular food and water, which a shed might provide, but they need quiet, too. They won’t make a nest in areas with high traffic, Mr. Combs said: “It’s abandoned construction sites or neglected areas within active sites, like a pile of supplies sitting idly for a month, that will draw them.”

For her debut novel, “The Next,” the author Stephanie Gangi made her protagonist a lair in a sidewalk shed. The main character was the vengeful spirit of a woman who dedicates her afterlife to tormenting an ex-boyfriend, and lurks in the scaffolding across the street from her old apartment. “I needed her to be hiding in plain site,” Ms. Gangi said. “I wanted her to inhabit a dangerous stretch that was also kind of intimate. With the weird black construction netting fluttering, it was the perfect home for a ghost. ” In real life, Ms. Gangi is an avowed scaffolding avoider; she’s not phobic, it’s the bottleneck of passers-by that irritates her. “We’re New Yorkers, you don’t just randomly walk. You stay in your lane. If I do get stuck under scaffolding, I direct traffic like a crazy person, ‘Stay to the right, stay to the right!’”

“People hate their fellow pedestrians in a scaffolding confinement more profoundly than they do once liberated,” said Dina Seiden, a Brooklyn-based author and comedian. “It gets very ‘Orange is the New Black’ under there.”

To Hannah Casey, a yoga teacher, scaffolding is an opportunity for athleticism. She showed me a photo of herself and Daryl K., a fashion designer, doing handstands on the scaffolding outside of Indochine a decade ago, midriffs bared. “We were outside smoking and there was the scaffolding,” she recalled. “It always makes me want to do gymnastics. If I was a pole dancer I’d really have a go at it.”

Greg Barton, an independent curator, is also a scaffolding booster. Two years ago, he organized a show about it at the Center for Architecture. He wanted to rebrand it as an experimental kit of parts, he said, instead of a necessary nuisance and eyesore. The exhibition displayed work by designers like Assemble, a British collective, that has used scaffolding to design temporary theaters or follies than can be built by novices. He included photographs of extraordinary bamboo scaffolding used in Hong Kong and Shanghai — intricate, handmade lacings that make supertalls look like ethereal baskets. He wanted to celebrate the labor that is often undervalued, he said. “Architecture with a capital A tends to privilege aesthetics over process. The immediacy and collaborative nature of scaffolding, its utility and functionality, is what appeals to me.”

“Scaffolding! A perennial topic,” Alexandra Lange, architecture critic at Curbed, wrote in an email. “I love it when building owners take the time to make their scaffolding feel like a place. Sometimes just a specific paint color or patterns can set a mood and make you feel as if someone cares about this transitional place. A full wrap with an image, purposeful graffiti, even a branded hue, it’s all better than peeling Hunter green paint.”

Toward the end of the year, the temperature dropped and my homeless neighbor hung a blanket from the scaffold brace over his bedding, shielding his camp. Down the block, the owners of Vapiano, a pasta joint, had wrapped the poles of the scaffolding outside their building with faux pine garlands and created a wall of ivy. A few blocks away, where scaffolding wrapped around the site of what had been a coffee shop, a middle-aged man had moved with his considerable collection of belongings, which included, mysteriously, a stack of broken skateboards. He put up a spindly, foot-high Christmas tree, nicely decorated. A few days later, he was gone.