HONG KONG - The scaffolding shudders as Sam Chan strides along an 8-foot-long bamboo pole positioned 50 floors above Hong Kong's bustling streets.

Twisting and pulling hard at a black nylon cord, he secures another vertical bamboo pole into place, his leg hooked instinctively around a fixed point. He's been making good progress with his crew in building this lattice in the sky.

"It's just a regular job," he said, glancing out briefly at the skyline behind him and the tiny ships gliding across Victoria Harbour.

Chan, a 34-year-old high-school dropout, has one of Hong Kong's most vertiginous and challenging blue-collar jobs.

He's one of around 4,000 scaffolding workers who spend their working lives dangling outside some of the world's tallest buildings.

The peculiar skills and mental traits required of a scaffolder have kept the profession relatively exclusive and well paid, despite a recent construction slump.

Wages range from HK$350 (US$45) per day for apprentices to US$100 for masters or "sifu" like Sam.

"(Scaffolding workers) have to possess physical endurance, courage ... and perseverance," says Chiu Kwok-leung, chairman of the Hong Kong and Kowloon Bamboo Scaffolding Workers Union.

"Can you imagine? We build from the ground up ... every day we climb upwards unceasingly. We need great determination."

HONG KONG TRADITION

The craft, which dates back centuries to the mainland, is not exclusive to Hong Kong. It is practised across China and in countries in Southeast Asia, including Thailand and Singapore.

But Hong Kong, with perhaps the world's greatest concentration of tall buildings, owes a special debt to the humble bamboo pole. Without it, few buildings could be finished or renovated.

Whilst the West prefers metal scaffolding, the great heights of buildings in Hong Kong make this a cumbersome, impractical option.

By using light, cheap and abundant bamboo cut from southern China, small teams of scaffolders are able to sheathe entire buildings in a matter of weeks.

Major engineering and construction advances through the years have failed to diminish the city's reliance on the low-tech pole.

"(We) have played a major role in Hong Kong's overall prosperity," said Chiu.

Scaffolding instructor Tang Sung-yuen says the trade will continue to endure, even as the city modernises.

"In Hong Kong, we will always be needed," he said.