Portable buildings are buildings designed to be movable rather than be permanently located in one place. Portable buildings are different in that they are often used in one location for a set period of time, and then taken away to be located somewhere else. Portable buildings are sometimes called modular buildings. The more common types of portable buildings are designed to be carried, usually in one piece, to and from the intended sites, being lifted on and off the transport vehicle by a large crane. The first known portable buildings were developed in 1955, and the first portable buildings, manufactured under the trade name Portakabin were built in 1961. Portable buildings can be stacked on top of each other, and sometimes brick cladding may be constructed around their exteriors to give them a more decorative look, or to fit in with their surroundings.