It’s not the kind of job that comes along often, but just in case you ever need to assemble a durable commercial floor from real pennies, here’s a brief tutorial from Silver Spring, Md., artist and designer Maggie O’Neill. She completed such a project for a popular restaurant in downtown Washington, D.C., two years ago.So far, O’Neill says, the completed floor has stood up well to heavy foot traffic, except for an area near the bar that was damaged by a water leak. And she’s finally stopped worrying about being arrested for violating the federal law against defacing or mutilating...

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