Abstract: An apparatus to assemble prefabricated walls and joist panels for homes, apartments, commercial buildings, etc. Apparatus is self-loading and can place and fasten 2.times.3, 2.times.4, 3.times.4, 4.times.4, and 4.times.6 cross members between parallel plates on the fly, having telescoping carriage and track, cross members may vary in length from 7-1/2 feet to 12 feet. Self-contained and portable apparatus may be used in remote locations and transported without special highway permits. All the frames for a building can be fabricated in on production run therefore saving handling and storage.