A single scaffold along a slope is used only for detecting problems by eye sight. A double scaffold with a work platform is necessary when actual work is to be conducted. Usually a platform is laid with wooden planks. In this photo, bamboos were used instead because it was more convenient to use bamboos in this situation. The government has published a guideline colloquially called “blue-cover book”, which requires the area of a work platform for building construction and renovation to be 0.4 meters in breadth. There is no stipulation for other types of work platform. Mr Chan recalled that a work platform had to be 4 to 5 metres in breadth for holding a large construction machine.