Maybe a wall to keep out the machines. From the current issue of Rolling Stone - The Rise of Intelligent Machines Part 2 by Jeff Goodell:
"If any company could be a poster child for how robots are transforming American manufacturing jobs, its Boeing. According to Reuters, Boeing is turning out 20 percent more planes, but with one-third fewer workers, than it did in the 1990s. In just this past year, it replaced hundreds of employees with 60-ton robots. Boeing says they work twice as fast as people, with two-thirds fewer defects. The impact of automation on the company's workforce has been dramatic. In 1998, the company made 564 planes a year, employing roughly 217 people per plane. In 2015, it made 762 planes, using about 109 workers per plane. Not surprising, a recent White House economic report concluded that labor productivity gains from robotics are similar in magnitude to the productivity gains from steam engines in the 19th century."