STUART MILLIS clings to a sheer rock face without a rope and only a crimp in the stone for a handhold. The climber's grip is slipping but he's in no danger - he's only a step off the ground. Millis is a proponent of bouldering, generally defined as scaling rocks without the benefit of ropes, harness or any equipment other than a bag of chalk and a pair of sticky rubber shoes. This isn't the daredevil-style free climbing depicted in the opening scenes of Mission: Impossible 2, though - the boulders are generally no more than a few metres high. Still, it's a wise climber who brings along a mat to cushion the inevitable fall. Previously seen only as practice for traditional mountain or rock climbing, bouldering has become a sport in its own right in Europe and North America and now shows signs of gaining traction in Hong Kong. 'You used to never see anyone out here climbing,' says Millis of the main bouldering sites at Ha Fa Shan, Lin Fa Shan and Shek Lung Kung near Tsuen Wan. 'It's only in the last couple years that you see [other climbers].' Climber Chung Kin-man, who helped pioneer bouldering in Hong Kong before going on to scale the world's toughest peaks, also reports more customers at his mountaineering store seeking referrals to bouldering sites. There may be as many as 500 people out climbing every weekend, he says. 'When I began climbing in Belgium and France in the early 80s bouldering was a brand new sport,' Chung says. 'It's totally different from being on a mountain; you don't need [equipment], just a chalk bag. We used to do it to get strong arms. 'After I came back, I started pushing bouldering. At that time it was all about rock climbing - Lion Rock and Kowloon Peak - and which rock was the hardest. So we started to push bouldering. And then some of the Brits started bouldering, too.' Enthusiasts extol it as 'climbing distilled to its purest form', more concerned with strength and agility than with the stamina required of a climb on a cliff face. That's among the most challenging aspects of bouldering and makes it most fun for Millis, who started climbing in his native England. 'It allows you to hone your skills without lugging ropes and equipment,' he says. Bouldering in Hong Kong became more organised a decade ago when a group of enthusiasts including Geoff Breach pooled their experiences to produce an unofficial local guide that climbers photocopied and passed along. They updated it in 2000 then Millis built on that information with his 2004 self-published guide, Hong Kong Bouldering, which he's now updating. At Lin Fa Shan on a recent weekend, Millis and a few friends warm up on the Lower Boulders and Summit Boulders, and then move on to Colin's Boulders. The last, he says, present some of Hong Kong's toughest climbing 'problems' - the term used for the part of the rock to be climbed. Problems are graded by difficulty, and of the several standards used, the V-Grade scale is more popular in Hong Kong. These start from relatively easy VBs and V0s to a nearly insurmountable V12. As is traditional, they're given colourful names and the problem Millis is clinging to is called Sparkie's Amazing Technicolour Dream Roof, a V5 climb from a sit-down start that follows a line of folds at the bottom of an overhang to the top of the rock. He clears the crimps at the bottom, but halfway up, where the overhang sees sunlight, fails to hold on and hits the mat. Part of the difficulty is the volcanic rock at Lin Fa Shan is far grittier than most. An engineering geologist by profession, Millis says more gravel and air bubbles had been trapped in its formation, creating a very jagged surface. Despite this, he starts again and, on his second attempt, clears the overhang to reach the top of the rock. Rather than make solving problems easier, climbers often strive to make them more difficult. Starting from a sitting position and hoisting themselves up to the rock is one way. Another is to attempt manoeuvres they would be foolhardy to try many metres off the ground such as dynos, or dynamic moves, that require leaping or swinging to the next hold. Climber Bon Man attempts the same route. He's shorter than Millis but powerfully built, and despite sporting injured fingers, lifts himself past the sit-down start and hangs on with a two-finger hold. But a long reach across the spur to the top face of the rock proves too far and he falls to the mat. 'That's a sandbag,' Man says, meaning the problem is perhaps harder than Millis has suggested. 'I'm afraid of heights. I prefer climbs that are short, difficult and low to the ground - like me.' Although considered safer than traditional rock climbing, done with ropes and harnesses, bouldering can be dangerous if a climber falls from a height. In Breach's guide to the sites, he notes how long it takes to reach the nearest hospital. However, rock climbing in country parks isn't regulated. Guidelines on the Leisure and Cultural Services Department ( www.lcsd.gov.hk ) relate only to the use of climbing walls at public sports facilities. Likewise, the Hong Kong Mountaineering Union, the sport's official body for certifying teachers, concerns itself mainly with roped climbing. For all the recent interest, Chung says the risks will stop bouldering becoming a mainstream sport. Hong Kong also lacks the extensive bouldering areas that Europe offers. 'It's not like Fontainebleau [in France], which has many routes. You can climb all day and feel very strong. But we don't have this kind of large area here.' Millis argues, however, that many sites have yet to be tried. His book alone lists some 500 problems from Tsuen Wan to Chung Hom Kok and Tung Lung Chau to Lamma, but enthusiasts are constantly posting new finds on his website ( www.hongkongclimbing.com ). There's no shortage of problems to engross newcomers such as Chu Sue-ling. 'It's relaxing. When you're on the rock you're totally concentrated,' says Chu, who joined Man on Lin Fa Shan. 'And it gets you outside. Going to a gym is boring compared with this,' she says, gesturing at the view of Tsuen Wan and the harbour. For Millis, too, there's a Zen aspect to the sport. 'You get tunnel vision in that you're 100 per cent focused on what you're doing. If you're not, then chances are you're going to fall.' Over the years, he's taken several spills, the worst being an eight-metre fall while bouldering and a 15-metre plunge while rope climbing. 'I've been very lucky in that I've not broken anything, at least not that I've been aware of,' he says. 'If I ever have my ankles X-rayed it might show that I've broken something in the past.'