Detailed overall plans of the Jiankou section and the restored parts in Huairou district spread across the office walls. They clearly show towers, checkpoints and various scenic spots Cheng has mapped using a computer program.

He has remained involved in providing technical guidance for the Great Wall's restoration with the Huairou cultural management department since he retired several years ago.

"Our main goal is to effectively eliminate safety hazards and reflect the ancient appearance of the Great Wall," Cheng says.

"Loose and naturally deteriorating parts have to be removed in time to avoid collapses and rainwater erosion, while (repair) materials should be applied as little as possible to follow the principle of minimum intervention," he adds.

Since 2004, Cheng and his team have overcome the precarious working conditions on the mountain ridge to restore multiple sections of the Great Wall that total roughly 20 kilometers in length.

In December, Wang was among the 10 people from all walks of life who were named "Beijing role model of the year" by the municipal publicity department.

Cheng still hikes up to this section of the Wall at least twice a week during the fieldwork season.

"I love the Great Wall to the point of obsession, and I know every blade of grass, every brick and every stone on it," he says.

He was born in a village in Huairou and began to learn tile masonry under the guidance of his uncle in 1972.

"At that time, being able to acquire a vocational skill was something to be proud of," Cheng recalls.