Scientists have devised a way to see through walls without any advance knowledge of the material they are made of. Besides having applications in the realm of security, the approach could lead to inexpensive devices to help construction workers easily locate conduits, pipes and wires. "Most technologies that can see through walls use a broad range of frequencies, which makes them expensive," said Daniel Marks, associate research professor at Duke University in the US. Since walls are generally flat and uniform in all directions, they distort waves in a symmetrical fashion. In their laboratory, the researchers constructed a couple of different kinds of walls and then placed objects behind them that a worker might want to find, like studs, electrical conduits, wires and junction boxes.