Why? Contour Crafting is a construction technology that potentially reduces energy use and emissions by using a rapid-prototype or 3-D printing process to fabricate large components. Comprised of robotic arms and extrusion nozzles, a computer-controlled gantry system moves the nozzle back and forth, squeezing out layers of concrete or other material to fabricate a form. The ultimate goal is to print a house in a day while drastically reducing material and energy consumption.