Profiled rail members (9, 10) with substantially uniform profile cross-sections, preferably for use in framework structures, comprise at least one interior wall (2) with a front side and a rear side, in the latter of which longitudinal grooves (6, 7) are provided, said grooves being defined laterally by upwards projecting wall and flange members (3, 4, 5), and are be joined in a mitre joint (26) by means of an assembling device comprising two fitting parts (19, 20) designed for substantially symmetrical arrangedement around the mitre joint (26) and having openings for an assembling joint (27, 28) for assembling the two fitting parts.
The profiled rail members (9, 10) and the fitting parts (19, 20) are provided with co-operating means (4a, 5a, 21, 24a) in order to cause, during said assembly, a simultaneous tightening of the frame profile members into mutually realigned positions towards the mitre joint (18, 26).