The shape of early prefabricated buildings was rigid and stereotyped. Later, people improved the design, increased flexibility and diversity, so that prefabricated buildings can not only be built in batches, but also have rich styles. In the United States, there is a type of mobile house, which is a relatively prefabricated building. Every living unit is like a trailer. It can be used as long as it is pulled in place by a special car, lifted to the floor by a crane, and connected to the built-in waterway, power supply and telephone system. The house is equipped with heating, bathroom, kitchen, dining room, bedroom and other facilities. Movable houses can not only form a unit, but also connect with each other.