Nineteen comics are huddled in a walk-in closet in the back room of a Chinatown beer bar, where comedian Ralph Cooper is running down a list of rules before he calls roll.

Basically, there aren’t any.

“Tell your rape jokes, your necrophilia jokes, your pornography jokes, your black jokes, your white jokes, your gay jokes, your Asian jokes,” Cooper says.

Any other night of the week, the back room at RFD could be mistaken for every sticky-floored sports bar in Penn Quarter. It becomes a make-shift comedy club when a worn, gray fold-up stage is wheeled out for Awesome Thursdays.

When it’s time to begin, Cooper bellows a deep-voiced welcome over the sound system. As he skips onto the stage, the spotlight catches the earring in his left earlobe. At 36, Cooper started doing stand-up in 2005 and co-founded Awesome Thursdays three years ago. He briefs the crowd the way he does the comics.

“This is a grown folks’ room,” Cooper says. “Look around. There ain’t no children. There ain’t no babies. For real, don’t get offended by people’s jokes. More importantly, please, please, please do not accost the comics about their views. . . . It’s jokes.”

For the audience, there’s just one rule at Awesome Thursdays, and the crowd dutifully shouts it in unison when Cooper asks them what it is.

“Shut the [expletive] up!”

In other words: Respect the comedians, some of whom are getting onstage for the first time ever. They’re “virgins,” in industry speak, “and we love our virgins,” Cooper says. His set is the first of the night. He riffs on how his baby son prefers metal to hip-hop, how the high school students he teaches during the day don’t realize they’re poor, and how smart people should have more children. Every comic gets five minutes, and the show usually runs more than two hours.

Most comics are pragmatic about the appeal of Awesome Thursdays. There’s a good sound system; it’s professionally run; if you’re on the list, you won’t get bumped; and it’s a short walk to the Metro. RFD is also a venue where you can try out any joke, no matter how filthy or abstract. That’s because Cooper and co-founder Brad Ryan run Awesome Thursdays for the love of comedy, without money getting in the way. “We don’t get a dime,” Cooper says.

“They also usually have a good crowd and it’s a good spot to tell friends to come check you out,” comedian Elahe Izadi writes in an e-mail. “And the guys who run it are supportive, especially of female comics, which I appreciate.”

When Izadi did a set at RFD the first Thursday of November, she joked about the dearth of trick-or-treaters dressed as Sojourner Truth on Halloween, what it was like as an Iranian girl to be called the wrong racial slur, and the fear that her last Twitter post before death might be something embarrassing.

Performers at Awesome Thursdays are young and old, Jerry Seinfeld-clean and Bob Saget-dirty. At one show, Cooper helped hoist a wheelchair-using comic to the stage. One regular performer has a stutter so severe that it interferes with the setup to some of his jokes. (He also writes around his stutter brilliantly, sometimes using it to soup up the pause before a punch line.)

“I’m very proud of the fact that at RFD we’ve had deaf people, we’ve had blind people, people in wheelchairs,” Cooper says. “We don’t deny anybody at all. That’s the one thing that makes me really, really, really proud.”

Although comics from all over the country seek stage time at RFD, shows have an intensely local undercurrent. There are jokes about hipsters at Howard University and crime in Baltimore. Politics come up, of course, but not as often as you might think in a venue that’s flanked by Capitol Hill and the White House. Cooper grew up nearby. He graduated from Robert E. Lee High School in Springfield, an experience that he says felt like a “crazy oxymoron” as a black student.

He has long been comfortable in front of large crowds. As a teen, he was ordained a junior pastor — “The church is way seedier than comedy. I’ll stick with comedy,” he now says — and became a star on the speech and debate team.

In his 20s, after Morehouse College in Atlanta, Cooper worked as an audio engineer in the music industry, then spent several years as a researcher and producer at NPR stations in Washington and Los Angeles, where he felt burdened by the lack of diversity. “It’s fair to say I had a confidence issue, meaning I had too much of that,” Cooper says.

In comedy, confidence and insecurity are inextricable. Stand-up is built on contradictions. Onstage authenticity can be both real and practiced, getting up there in the first place is an act of dueling courage and vulnerability. The best jokes have sucker punch lines — they hit you before you see them coming, and surprise you into laughing.

Philadelphia-based comic Dave Temple was the last one to take the stage the night he came to RFD. He didn’t know quite what to expect, but he quickly came to feel the audience’s passion for comedy with any gimmickry. Sporting jeans and a navy zip-up Ralph Lauren hoodie, he immediately pointed to a man in the crowd: “You’re wearing shorts? You and I clearly wear 70 degrees very differently.”

He talked about wanting to take money out of his retirement account to put rims on his truck, and drinking so much one night that he tried to tip a cashier at 7-Eleven. “How [expletive] drunk do you have to be where it’s just like, ‘This is for the hot dog. Take a little something for yourself.’ ”

The vibe at RFD is unusually supportive. “That’s rare and special,” Temple says. “I love finding rooms like this.” Hecklers materialize, but the crowd is mostly comedy geeks buffered by friends and family.

The space works as a comedy laboratory for both rookies and veterans because if a joke kills in a roomful of comedy lovers, it’s a fairly good indication that it will make a mainstream audience laugh. That’s part of why the room feels right even when a set is messily, unpredictably falling apart.

Stand-up, like group therapy, can be cathartic for everyone involved. At its most refined, stand-up comedy is a wickedly precise exploration of the intersection of truth and absurdity. The old equation is comedy equals tragedy plus time. But ultimately comedians go onstage because they want to be liked.

“It is totally ego, it’s totally ego, it’s totally ego,” Cooper says. “Nobody gets up on stage and makes people laugh because they feel like they’re socially redeeming. We really created the room for one reason and one reason only. We wanted to have a room where — black, white, it doesn’t matter — if you are funny, come to the room. If you want to do comedy, come to the room.’’