National Archives Special Police Officer Terry Walton gives a briefing of the rules and regulations to a group of tourists at the National Archives. (Ricky Carioti/WASHINGTON POST)

The crowds brush by the Magna Carta — there’s too much Britain on television, anyway — and instead wait quietly for their 20-minute romp with Washington’s most-prized Americana.

A flock of 50 patriots —children, retirees, a lone government bureaucrat on a long lunch break — gather at the base of the Rotunda in the National Archives, waiting for their signal to approach the Charters of Freedom.

A security guard walks to the center of the steps. He begins an address using the seven-story dome for acoustics.

“I know the question you’re wanting to ask,” he says to the boy at the front of the mob. “Was ‘National Treasure’ filmed here?’

This crowd laughs and perks up, just as tourists did yesterday and the day before.

National Archives Special Police Officer Janet Sharp, top right, looks on as tourists view the Constitution at the National Archives. (Ricky Carioti/WASHINGTON POST)

“Well, no. ‘National Treasure’ was not filmed inside here,” he tells them, before launching into a masterful soliloquy about the Constitution, the Declaration of Independence and the Bill of Rights. He tells them the details to look for — the handprint, the signatures — and preempts their questions before they can wonder aloud in the Rotunda.

Who’s the guy in the painting with the wooden leg?

Gouverneur Morris.

Why is the Declaration of Independence faded?

Because it was on display in harsh light for much of the 19th century. So, no cameras.

Are you sure there isn’t a map on the back of the Declaration of Independence?

Yes. We’re certain.

Security guards answer these questions with color and context — with the knowledge one expects from a historian or docent. But the dozen or so stationed at points around the Rotunda receive no formal training from the Archives.

There’s no reason these guards should know the answers to tourists’ questions on history and architecture. Their mandate is simple: Protect America’s founding documents. But since they work in this dimly lit shrine to America’s founding charters, they speak tourist fluently. They anticipate the queries and read up on the history. They know when tourists are too ashamed to ask who wrote the Constitution.

“There’s a routine we go through up there,” says Robert Pringle, 71, a guard with American Security Programs, the contractor the Archives uses. Pringle has worked in the Rotunda for 16 years, beginning his career before the Archives got a boost from a Disney’s historical fiction blockbuster.

“I call it ‘that movie,’ ” Pringle says of the “National Treasure” film franchise that kids ask about daily. “We get a lot of questions about the filming.”

But Pringle receives other questions, too, and he uses his position to educate the crowds.

“People are surprised to hear that the documents were written on parchment, not paper,” he says. “Sometimes they’ll try to read the cursive and they’ll give up after the first few lines.”

“Some of the questions stump us,” says Bryant Bethea, 38, a security guard who’s worked at the Archives for 13 years. “A kid once asked the distance from the floor to the top of the dome, and I didn’t know, so we had it measured. It’s 73 feet.”

Tourists also love to give their opinions.

“Sometimes tourists will say, ‘Our congressman should come here and look at the Constitution,’ ” Pringle says of the political banter he hears. “We don’t comment on that. . . . It’s always so moving, though, when tourists have an emotional response to the documents. You’ll see them with tears in their eyes.”

Besides the security guards, a trained group of volunteers and docents at the Archives also takes visitors around the Rotunda every few hours. The guards hear so many of these tours that they pick up anecdotes naturally.

“A synergy develops among the volunteer docents and the security,” says Rebecca Martin, volunteer and tour coordinator for the National Archives. “Stories and anecdotes get passed along all the time. Everyone is borrowing stories and spying on what everyone else is saying.”

Which is great for the tour guides, since the Archives building is open seven days a week, nine hours a day during the summer. On its busiest day this year, the Archives received more than 5,000 visitors. With a million visitors annually — many coming in the summer months — it’s hard to answer every question. Martin says that informed and friendly security guards are a valuable asset.

“We try hard to make sure that visitors have the opportunity to learn as much as they’d like to in our public vaults and our learning center,” says Martin. “And people are really curious. We’re always delighted to answer questions.”

Even those tired, obvious questions about “that movie.”

An occasional series about the arts in Washington and the visitors who admire it