File photo shows the Luofeng wooden-roofed arch bridge in Xiadang town of Shouning county in Ningde, east China's Fujian Province. (Photo: China News Service/Wang Dongming) Instead of using building materials such as nails, the bridges were built using the mortise and tenon joint process, a concavo-convex connection method used to combine two pieces of wood. Bridges built with the application of such techniques are able to withstand the hazards of flooding and stand strong even after 100 years of service.

File photo shows the Luofeng wooden-roofed arch bridge in Xiadang town of Shouning county in Ningde, east China's Fujian Province. (Photo: China News Service/Wang Dongming)

File photo shows the Shuanglong wooden-roofed arch bridge in Xietan town of Shouning county, Ningde, east China's Fujian Province. (Photo: China News Service/Gong Jian)

File photo shows the Sanxian wooden-roofed arch bridge in Hexi village of Chunchi town, Zhouning county, Ningde, east China's Fujian Province. (Photo: China News Service/Li Hongyuan)