Two skyscraper cleaners hover in the high sky at the 101st floor of Shanghai World Financial Center to test their equipment before cleaning the building’s exterior windows on March 26, 2012. To clean the tens of thousands of glass windows, more than 30 cleaners use the special contraption. The cleaners are prohibited from taking watches and cell phones up, and all work is stopped when wind speeds exceed safety levels. [Photo/CFP]

A skyscraper cleaner works on the windows of the 94th floor of Shanghai World Financial Center on March 26, 2012. [Photo/CFP]