Only a few weeks after the first of what would become near-daily Black Lives Matter protests in New York City, Justina Heckard found herself on her bicycle in Brooklyn, leading a march in loose formation with other cyclists. An altercation with a driver left a protester injured, and Ms. Heckard and her fellow demonstrators decided they would need to sharpen their tactics.

As protest organizers learned to handle everything from physical confrontations to dehydration, they developed strategies and clearly defined roles designed to keep marches on track and participants safe.

Some of these tactics, however, can put protesters in direct confrontation with both the police and bystanders.

Heres a breakdown of some of the most common roles.

At a demonstration last month, Larry Malcolm Smith Jr., noticed a female protester quarreling with a photographer. She had told the man that she didnt want to be photographed, Mr. Smith recalled. Although he had a right to photograph in public, the photographer seemed to be unusually aggressive.

As a marshal, Mr. Smith, 21, was there to make sure that the demonstration ran smoothly. He intervened in the argument and told the photographer to move away from the woman.

Mr. Smith said he tries to pay attention the needs of Black women. There needs to be more Black men that come out and show up for Black women, he said.

Marshals tend to be scattered throughout a march often equipped with bullhorns and are there to answer questions and keep the energy alive in the middle and back end of a protest.

Born in Jamaica, Queens, Mr. Smith began protesting at age 8, after Sean Bell, an unarmed Black man, was shot by plainclothes officers in Mr. Smiths neighborhood.

I dont feel like I chose activism, he said. Activism chose me.

In early June, Justina Heckard, who works as a music manager, took her bike to demonstrations as a social distancing measure. She said she was soon asked to help divert traffic along with other bike protesters.

At a march on June 6 in Crown Heights, Brooklyn, Ms. Heckard, 32, and a dozen other cyclists pedaled ahead to clear a route. It was there, she said, that they crossed paths with a motorist who refused to take another street and threatened to drive through the incoming marchers.

With their fellow protesters approaching, the cyclists didnt know how to respond. One stood in front of the car, as shown in a video of the incident, and another tried to jump on the cars roof.

A few seconds later, Ms. Heckard said, the driver accelerated, injuring one protester. That night, demonstrators realized bicyclists needed to be better prepared if they were going to be the first line of defense against motorists.

Now, bike blockers work to de-escalate tensions when they meet uncooperative motorists and form tight lines to block traffic.

This tactic, however, is technically not allowed without a permit, which most protests lack. For the safety of all New Yorkers, we cannot support any blocking of traffic that is not authorized by a government agency, said a spokeswoman for the Police Department.

The danger posed by bike blocking doesnt concern Brandon English, 31, a visual artist. Growing up in Cobb County, Ga., Mr. English recalled being heckled and verbally threatened by white drivers on his way home from school.

Thats something thats been understood for me as a Black person in the United States, Mr. English said. Whether Im protesting or not, my life can be in danger.

Robert Thorne was volunteering at the medical tent at Occupy City Hall in July when he heard that a protester on the Brooklyn Bridge had sustained a head injury after falling off a bike. Mr. Thorne, 33, who has a background as an emergency medical technician, got to the bridge before the ambulance and tended the protesters wounds.

Now, along with his wife, Laney Thorne, 31, he joins protests across the city as a street medic, walking along the edges of the march, ready to treat wounds and help people exposed to pepper spray.

Street medics carry backpacks, usually marked with red crosses, stuffed with first-aid supplies.

Mr. Thorne and his wife came to New York from their home in Elkhart, Ind., after they both lost their jobs because of the pandemic.

Mr. Thorne said his commitment against police brutality had intensified after helping as a street medic: If this goes on in the wintertime, Ill be out there, said Mr. Thorne. I have no intention of stopping any time soon.

Kevin Mora, a lab technician, joined protests as a street medic in May. But in early June, while helping a protester who was exposed to pepper spray, Mr. Mora searched through his backpack only to realize he didnt have any water with him. As he began to panic, a protester from a supply crew rushed over with a bottle of water.

Mr. Mora, 23, said it made him realize there was work to be done at protests aside from moments of crisis, and led him to start Your Fight Too, a mobile bodega that provides supplies everything from masks, food and water to feminine hygiene products.

Mr. Mora, who is Ecuadorean and bisexual, grew up in a culturally homogeneous town Easton, Conn., said his participation in the protests had made him question what it means to be an ally: Ive been re-evaluating the word..

He used to be more concerned, he said, with how others were being allies for him.

Now he asks himself: How have I been an ally in return?

At a demonstration in August, Erica Johnson, who attended as a legal observer, watched as officers approached two protesters who were driving behind the march to help control traffic. She started recording the interaction in her notebook. One of the officers who had approached the car noticed Ms. Johnson and then walked away.

Legal observers attend demonstrations to document interactions between protesters and police officers. They also connect protesters to legal representation and help those who are arrested.

Civilian observers are allowed, according to the New York Police Departments Patrol Guide.

We welcome legal observers and encourage their coordination, a police spokeswoman said in an email. Still, legal observers are subject to arrest: At a June 4 demonstration, nine legal observers were arrested.

Later that month, the police commissioner, Dermot Shea, defended the arrests during testimony before New Yorks attorney general, Letitia James.

Having a shirt or a hat that says legal observer doesnt mean theyre an attorney, Mr. Shea said, or theyre actually performing any legal functions.

Ms. Johnson is a brand manager at a marketing company and has been volunteering with the National Lawyers Guild for nearly a decade. She said she had noticed a greater demand for legal observers at protests in recent months.

Especially when its my own community, I feel like I have to show up a lot more, she said. I feel like I cant do enough.

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From Bike Blockers to Street Medics: The Anatomy of an N.Y.C. Protest - The New York Times