When he was 10, Yan Cong started patrolling the border on his own.

One dark night when Yan Cong tried to clear the trail of thorns in the rain, he accidentally cut his own leg. It aches sometimes, even now, because it took time for him to get treatment. However, he has no regrets.

"The first time I patrolled the border with my father and the border police officers when I was 6, I complained that the trail was very long. Dad told me that it was endless and encouraged me to keep going," Yan Hu said.

A one-way journey takes around six hours. When the men get hungry, they eat compressed biscuits, and they play instruments and listen to music while taking a break.

"When we pass the stone boundary markers, my father always asks me to touch them. When I do, it's like I can feel his efforts and those of my grandfather, and their devotion," Yan Hu said.

In 1993, Yan Cong saw the installation of boundary markers No 180 and No 181.

On patrols, he often tells the history of each boundary marker to the other officers and stresses the importance of guarding the border to younger members.

"In my eyes, my father and grandfather are both ordinary people but also heroes," Yan Hu said. "I will carry on the mission and patrol the border with my father."