Formally, railings can be divided into inter-section and continuous. The former consists of a column, an armrest and a crosspiece. The handrail is supported on the column; the latter has a continuous armrest composed of an armrest, a railing and a base. Common types are: wooden railings, stone railings, stainless steel railings, cast iron railings, cast stone railings, cement railings, modular railings. Generally, the low column height is 0.2 to 0.3 meters, the middle column is 0.8 to 0.9 meters, and the high column is 1.1 to 1.3 meters. The inter-moment of the balusters is generally 0.5 to 2 meters.