Completed prayer stones displayed at the stall.

Olo Tsering headed to Tibet's regional capital Lhasa two decades ago. He has dabbled in various kinds of work but finally chose to focus on prayer-stone carving.

His pieces include various Buddha images and Tibetan scriptures, such as the famous Om mani padme hum, the mantra of the bodhisattva of compassion, Avalokiteshvara.

The craftsman said the carvings are an important part of Tibetan culture.

"I am the third-generation prayer-stone carver in my family and I hope this tradition will last forever," he said.

Olo Tsering said he has trained more than 10 apprentices, including his son.

"Prayer-stone carving dates back about 1,300 years. It is like a venerable river and I don't want see to it drying up one day," he said.

Olo Tsering's son is in middle school and he trained the boy during the school holidays.

It takes about two years to become a qualified prayer-stone carver, he said.

"Learning how to carve the scriptures requires at least two months. It takes two years for the images," he said.

Olo Tsering said carvers also have to be religious. They must desire to inherit the traditional art, be able to read and write, and work diligently.

Carving a long mantra takes a long time and much energy. A short work of four to six syllables requires several minutes.

"The shortest mantra has four syllables, and I can carve 300 to 400 plates in one day," he said.