"What a fence is doing

"What a fence is doing 90 percent of the time is telling someone not to go here," says Mark Davis, president of the American Fence Association. "A fence will stop a pretty honest person. But anybody with a tool or ability to get in will get in."

"It's something designed to get you angry," says Jamie Loughner, a protester from Washington who joined the Medieval Bloc in Quebec City. "People become more outraged because they are so offended by the fence. . . . It's easy to shake your focus from what you're truly protesting."

"It gives you a very clear boundary, that people have in fact breached the law," says Thomas Seamon, a law enforcement consultant. "People are going to actively either climb over it or attempt to rip it down. Then there's no question you've broken the law."

"If you can make the fence a target so police aren't the target, or private property is not the target, or individuals are not the target, then this fence would have served its purpose," says Hubert Williams, president of the Police Foundation, a District-based outfit that provides research and technical support.