"It's of utmost importance to inherit and pass down the things left by our ancestors while not changing the original craftsmanship to leave real things for future generations," he says.

He started to work on the Jiankou section in 2016. The toughest stretch slopes to nearly 80 degrees, and the places for walking are only a few inches wide. It's called Yingfei Daoyang (Eagle Flies Upside Down), suggesting that even an eagle would have to soar vertically, with its beak pointing up directly toward the sky to fly over this spot. Most parts of the Wall here were about to collapse before the restoration, and about 40 meters of the fortification had tumbled into a trench dozens of meters below. Neither people nor mules could move the stones, which weighed hundreds of kilograms, Cheng says.

He overcame the problem by instructing the workers to use a winch to hoist the stones back into place. Each took six or seven attempts.

After years of efforts, the slope has regained its historical appearance, without any traces of repair.

Cheng says he feels proud whenever he steps on the solid and steady ground on the Great Wall without worrying about the bricks falling off anymore.

Zhao Xiaojie has worked side by side with Cheng since 2004.

"During work, he is our leader. But off-duty, we hang out like brothers," Zhao says.

"Cheng is meticulous when it comes to work. If something is not done well, he insists on redoing it. He has a real affection for the Great Wall, and he tirelessly guides the bricklaying and the rest of the work in person … nothing seems to be able to keep him from the Great Wall."

Cheng says he's grateful to receive the Beijing role model recognition.

"It's a great honor for an ordinary person in an ordinary post, which encourages me to continue," Cheng says.

"Protecting the Great Wall is my responsibility. My physical strength is still adequate. As long as I can climb up the mountain, I'll do my best to lead my team, especially to assist them in accumulating experience and making their due contributions."