Cleaning the external walls of buildings has become a profession as thousands of tall buildings have sprung up alongside China's rapid development urbanization program since the implementation of the reform and opening-up policy about four decades ago.

A recent report issued by the Council on Tall Buildings and Urban Habitat in Chicago showed that China accounted for 56 of the 106 completions of 200-meters-plus buildings globally last year.

The job attracts many migrant workers because it offers higher salaries than other cleaning work. The workers need to complete a training program and obtain a special operations certificate. The work exerts mental and physical pressures on the workers.

Although they take a lot of protective measures, there are still a lot of dangers in high-altitude working.

The cleaners are harnessed to a safety rope when working. They often allow the rope swing in a wide arc so they can clean as large area as possible. These wall cleaners are often called "Spidermen".