LANZHOU, July 2 (Xinhua) -- Woodworker Sun Gang has spent most of his life learning and preserving the traditional mortise-tenon joint structure technique, widely found in ancient Chinese buildings and furniture.
In ancient China, buildings contained no nails, and were instead built using the mortise and tenon joint process, a concavo-convex connection method used to combine two pieces of wood.
The earliest mortise-tenon structure example dates back 7,000 years to the Hemudu culture in China's Zhejiang Province.
"The mortise-tenon structure is our ancestors' great wisdom," said Sun.
Born in a village in Gansu Province, 52-year-old Sun dropped out of elementary school after just three years.
Under his father's instruction, Sun acquired carpentry skills and began to do woodwork at 13.
"At that time my family was so poor we could barely afford any furniture or tools," Sun recalled. "But my father and I made ploughs, wood tables and chairs by ourselves."
"It was hard to find iron nails. Instead, my father taught me how to make simple mortise-tenon joints and use them to assemble little gadgets," Sun said. "It was then that I fell in love with the craft."
Sun has had quite the journey to go from simply a fan of mortise-tenon structures to preserving an intangible cultural heritage.
In 1987, Sun left home to look for work in neighboring cities as a decorator and furniture maker.
After ten years of hard work, Sun had saved a large sum of money and honed his carpentry skills. In 1998 he returned home and started his own business - producing modular furniture in large quantities which was then popular in the market.
However, Sun found almost no furniture used the mortise-tenon technique anymore, with nails and glue being used for large-scale industrial production instead.
"Traditional redwood furniture made with mortise-tenon joint structures is known for its shape, curve and technique," said Sun.
After conducting market research in Shanghai and Guangdong, Sun surprisedly found that his idea had huge market potential.
His first sale was for 6,000 yuan (about 900 U.S. dollars), selling a wooden round-back chair with mortise-tenon joint structure.
In 2014, Sun set up a company to specially produce and sell tailored cultural and creative products including furniture and wooden handicrafts featuring mortise-tenon joints.
In Sun's 300-square-meter factory, he displayed just how strong the wooden joints are by putting his entire body weight on a hand-made wooden arch bridge but it didn't even move.
"Those marvelous mortise-tenon joints enable the wood bridge to carry a weight beyond our imagination," said Sun.
"Wooden components are perfectly joined together without nails and can stay firm for thousands of years," Sun added.
Among his woodwork, Sun was very proud of a pair of wooden vases. "The components fit each other perfectly and you cannot see a single tiny crack. The vases received an offer for 400,000 yuan, but I did not sell them," Sun said.
In 2017, the company had sales of more than 1 million yuan.
Throughout Sun's career, he has always believed that this ancient technique should be passed on to younger generations so more people can know about it.
"Classic traditional art is permanent and must be better preserved," said Sun, who was chosen as one of the preservers of the provincial intangible cultural heritage in Gansu in 2017.
Sun has shared his skills with more than 10 people including his son Sun Yacheng who sees his father as a great inventor.
"It is a hard job to make mortise-tenon structures, but my father succeeds because of his intelligence, even several senior engineers cannot do what he does," said Sun Yacheng.
"It is not easy to maintain inner peace and tranquility in today's busy world, but dealing with the mortise-tenon joint structure can help you," said senior Sun. "Believe it or not, I can spend hours working on a piece with the traditional joint structure."
To better spread and share the mortise-tenon craft, Sun Yacheng has his own plan.
"I will use mortise holes and tenon tongues to design new interactive toys for children," he said.
"Interactive toys are a good way to develop children's intelligence and help with their dexterity," said Sun Yacheng. "They can also learn about craftsmanship while playing games."