Abstract: An assembly system for modular building units having a floor and a plurality of walls is provided. The assembly system includes a floor platform, a plurality of wall platforms, and a plurality of hinge assemblies. Each of the plurality of hinge assemblies may be rotatable to at least a first position and a second position when attached to the floor and the one of the plurality of walls. In the first position, the walls and the floor are generally parallel while in the second position the wall and the floor are generally perpendicular. Methods of use are also provided, in which, during use, the hinge assembly of the system may be rotated from the first position to the second position at least in part by moving the walls in an upwards direction relative to the floor.