Many forms of housing have been designed and built in the United States. Be aware that the terminology used to identify and describe the various forms of housing is by no means standardized. In contemporary usage, the term "townhouse" is sometimes used by real estate promoters for almost any form of row house, thereby taking advantage of the prestige of housing from an earlier era. A distinction can be drawn between the "conventional" and the "factory-built" method of building housing. The width of the selected module depends on the design of the housing, and on regulations that set the maximum width which may be transported on state highways. Once the home is delivered to its intended site and placed on its foundation, the wheels used for its over-the-road transportation are removed and the home takes on the appearance of conventional housing. Panelized housing consists of housing constructed from building components such as factory-built wall panels, roof trusses, and floor trusses.