In stick construction, the curtain wall frame is constructed mainly on-site with mullions and transoms supporting glass, spandrel panels, metal panels, and brise-soleils, connected piece by piece. Each mullion is usually supported by the floor or perimeter beams.
In unitized construction, on the other hand, the curtain wall is composed of large units that are assembled in the factory, shipped to the site, and erected on the building. Aluminum profiles are used to form the frame, which is normally one-story high. Opening vents, glazing, and infill panels are built into units before being transported to the site. As with stick construction, each unit is usually supported by the floor or perimeter beams.