AFTER two days of work, the mound rising centre-stage at the Hongkong Coliseum has been raked and pounded into shape ready to hold the weight of the 40 sumo wrestlers competing in the territory's first tournament at the weekend. Known as a dohyo, the platform on which the wrestlers will tussle is made of two eight-tonne truckloads of New Territories soil mixed with cement and shaped by an eight-man team, including five ring announcers, or yobidashi. Overseeing the construction is Masahiro , who has been building dohyos in his role as a yobidashi for the past 30 years. The condition of the dohyo plays an important role in determining the professional fate of a sumo wrestler and Masahiro painstakingly monitors the construction and ratio of materials used. ''The most important thing in a dohyo is it has to be firm and quite hard to protect the wrestlers from injury,'' Masahiro said. Although a traditional dohyo uses soil alone that is dried slowly to a firm surface, in the world of touring sumo where temporary rings must be constructed in a couple of days, traditional methods have been supplemented by modern materials. Masahiro has mixed about four bags of cement with the soil to ensure the soil sticks, holding its shape, and dries firmly. The six-square metre-platform has been padded in its centre with cardboard boxes and the edges are bound by hessian cloth to hold the shape - a technique developed about eight years ago for tours. After being raked flat, the soil is pressed by foot before two men pound the dohyo smooth using a heavy wooden mallet. The 4.5-metre circle limiting the wrestlers' movements is then marked with straw bundles. The first bout begins at 6 pm tomorrow.