There was one bright light on inside Jimmy Valentine’s Lonely Hearts Club, a bar on Bladensburg Road NE with no sign and no phone number. Usually the place is so dark it takes a good 30 seconds for your eyes to adjust when you step in from a sunlit sidewalk. A dim, red glow fills the room, where the vodka bottles are lined up beneath a shelf of skulls. The drink of choice, advertised on the bar, is a Mr. Lethal, a “delicious but deadly” concoction.

On Monday, a single bright bulb illuminated a cluster of about 10 women huddled in a banquette by the front door.

They were knitting.

Pink and red hearts fluttered to the floor as the women, ranging in age from about 25 to almost 70, worked their way through piles of yarn carpeting the ground.

The knit-in was in preparation for what Beth Baldwin, the organizer of the night, was sure would be “the biggest yarn-bombing that’s happened in D.C.”

Yarn-bombing is like grandmotherly graffiti; instead of tagging a building with spray paint, yarn-bombers leave their mark with knitted objects. The movement has been gaining momentum. Last July, a horse statue outside Hard Times Cafe in Alexandria was given knitted leg warmers, a big blanket and other winter accessories. Baldwin has noticed similar small acts of subversive crochet: a sleeve for a tree trunk in Mount Pleasant, an International Yarn Bombing Day declared on Facebook for June 11.

Perhaps the most notable installation so far took place in New York City when the “Charging Bull” sculpture on Wall Street was outfitted by Agata Oleksiak in December 2010. Oleksiak has referred to her work as art, not yarn-bombing or graffiti.

“I would not put yarn-bombing in the realm of graffiti,” said Rebecca Stone Gordon, who participated in the Jimmy Valentine’s and Hard Times yarn-bombings. “Simply because . . . the work is easily removable. It’s not attached to the structure in a permanent way or in a way that damages the structure.”

Whereas graffiti can permanently change something from its original state, yarn-bombing temporarily beautifies ordinary objects of everyday life.

“People place it in the ‘cute’ category because it’s the realm of women’s crafting,” Gordon said. Yarn-bombing “is nonaggressive. . . . You subconsciously know, looking at it, that a cozy on a tree is safe for the tree.”

Baldwin’s plan for Jimmy Valentine’s was to yarn-bomb the bar’s storefront by plastering the wall with knit hearts. A place that’s usually impossible to spot was set to become a stop-and-stare destination.

The catalyst for decking out Jimmy Valentine’s was Julia Christian, the executive director of CHAMPS Capitol Hill’s Chamber of Commerce, which produced ARTventures on H, a celebration of the arts in Northeast Washington’s H Street Corridor. Thirty-seven galleries, theaters, bars and restaurants signed on for the event, including Jimmy Valentine’s.

“I knew we needed to come up with something really cool for Jimmy Valentine’s,” Christian said. She contacted Baldwin, a friend and “phenomenal crafter,” and asked for an out-of-the-box idea.

“How about yarn-bombing?” suggested Baldwin.

“I looked it up and said, ‘Oh, my God, this is exactly what we need to do,’ ” Christian said. “It’s very wacky and very cool at the same time.”

Once Mark Thorp, the bar’s owner, found out what yarn-bombing entailed, he was on board. “If it’s creative artistic output, we’re in.”

On Thursday, the day of ARTventures, Baldwin knelt in front of the door at Jimmy Valentine’s, weaving hot-pink yarn through its grates to tie one of 101 hearts on display near the handle. Just as she planned, hearts of all sizes covered the storefront in a giant collage. Perched above the hearts display was a life-size model of the Jimmy Valentine’s logo, a skeleton with wings that dangles a heart on a string. The wings, made of cut-up sweaters sewn together like shingles, spanned 12 feet.

“I used to drive up and down Bladensburg two times a day for years,” Baldwin said. “It was rough. I had firecrackers thrown at my car. The thought of doing something cozy on this street really appealed to me.”