Wooden columns must be made of logs with a diameter greater than 300 mm, without corrosion, fracture marks and moth-eaten.
The installation of wooden columns requires that the big head is down and the top is compacted with a wooden wedge. The number of wooden wedges shall not exceed two, and the number of layers shall not exceed one.
The point column must be placed on a solid foundation, and it is forbidden to be placed on silt and floating coal. When the bottom plate is muddy, it must be padded under the column and supported firmly.