WASHINGTON — With a little bit of rap (about King George III, of all people: "He was a meany and we were so teeny"), a healthy but not overbearing dose of history and a whole lot of nerve, two recent college graduates are rattling the genteel world of Washington tour guides.

Ben Hindman and Brody Davis are giving tours for free.

Working only for tips, the two friends in bright orange caps are attracting tourists who find themselves on the National Mall knowing little more than that the really tall one has to do with Washington; the squat, columned one is where Forrest Gump liked to hang out; and the one with the dome is where the president lives, or something like that.

"A lot of tourists really don't know anything about Washington or history," Hindman says. "We thought we could entertain people and get them interested in history at the same time."

Not entertained are the city's professional guides, who "really don't like us," says Hindman, 24, a Bostonian who found the inspiration for DC By Foot in Berlin, where he took a tour from a tips-only guide.

"This has been their livelihood, and they don't like us giving it away," Davis says. "They are professionals, and they think we don't know anything."

Actually, says Tom Whitley, who handles marketing for the Guild of Professional Tour Guides of Washington, D.C., "it would be foolhardy for highly skilled guides to get into some kind of a fight with people trying to pick up tours out on the street. Let's just say that it's much more likely that a person who wants a qualified guide will go out and get a professional guide."

The guild's code of ethics frowns upon soliciting for tips. Hindman and Davis figure their business is the ultimate expression of capitalism. They offer a service; people determine its value and pay accordingly.

Although traditional guides say they provide accurate and compelling stories about Washington and the nation's great symbols, the two buddies fresh out of Vanderbilt University say they checked out the competition and were underwhelmed.

"We went on the other tours, and they were really pretty boring," says Davis, 22, who worked as an intern for senators Bill Frist and Joe Lieberman before diving into the tour business.

So Hindman and Davis studied up, obtained D.C. tour guide licenses and asked their former history professors to share favorite Washington stories.

They concocted a script mixing the standard tales of heroism and nation-building (the birth of lobbying at the Willard Hotel, the stirring John Adams-Thomas Jefferson friendship, the strange but true explanation of why the Washington Monument is two-toned) with wacky bits that would probably come only from the minds of kids fresh out of college.

For example, your average professional guide, while summarizing the Revolutionary War, probably doesn't ask tour groups to "march like you're British" and lead the tourists skipping down the path.

"More than anything else, I want the tour to be factual," says Davis, who recalls hearing guides on other tours tell about how when the elevator in the Washington Monument first opened to the public, authorities tried to overcome public fears of the newfangled machine by offering free whiskey to any man brave enough to ride the car up and back.

Davis says he "found out there was no way the government would offer whiskey to people and no ban on women and children riding the elevator."

So Davis instead tells the (true) story of Gabby Street. On an August morning in 1908, the catcher for the Washington Senators caught a baseball dropped from the top of the Monument, pocketed a $500 prize, walked away dazed by the impact and went on to catch Walter Johnson's pitching in a 3-1 victory over Detroit that day.

If the professionals are disturbed by the introduction of free tours on the Mall, they are smart enough to keep their carping to a minimum, in part because they don't think the free model will survive. Hindman and Davis sometimes have their doubts, too.

Since they started last summer, they have given more than 100 tours, averaging more than 35 people per outing and collecting about $150 from each group. A family of four is often happy to fork over a $20 tip rather than the $15 per person — or much more — they might have to pay for a traditional tour.

"That paid the rent and let us hibernate for the winter," Hindman says. Along the way, they figured out that foreigners tip better; that the larger the group, the lower the per capita tip; and that nothing gins up business better than making nice to hotel concierges. (This is, after all, the capital of lobbying.) But some concierges prefer to recommend only tours that deliver a commission for sending business their way — a step the DC By Foot guys say they can't afford.

For now, Hindman and Davis are getting by. They'd love to turn their business into a permanent fixture on the Mall, but they're hedging their bets. Davis plans to go to law school, and Hindman to business school. Turns out there's something to this idea of being a professional.