This invention relates to an apparatus for assembling roof trusses. Known apparatus suffer from the drawbacks that the erection or preparing of an assembly jig before truss fabrication can begin is cumbersome and time consuming. The above problems are solved by providing a multi-section assembly table with narrow, parallel, elongated openings (20, 20a, 20b, 20c, 26, 27, 28, 29) in each section. Jig stops (31, 32, 33, 34) are individually adjustable along these openings (20-29) by respective lead screws (51) driven by stepper motors (47). The motors (47) are controlled from a computer (132) to automatically position the jig stops (31-34) in accordance with a particular truss design. The apparatus has conveyor roller carriers (61) between the sections of the assembly table which are raised to lift a completed truss up from the table, so that it can be slid off the table.