Abstract: An extruded aluminum alloy rail for supporting a shaft for a linear guidance system, the rail comprising a vertical body with a longitudinal notch on its upper surface for receiving the shaft along two generatrixes and a pair of symmetrical longitudinal wings at its base for resting on a fixed stand, the wings being configured so that only the smallest possible surface areas of the wing rest on the support supporting the rail which together with bushed ball bearings support shafts for assuring the linear guidance of high precision modules or mobile platens.