Abstract: A positioning apparatus in which a runner is arranged to travel backwards and forwards by way of a threaded spindle extending in the lengthwise direction of the apparatus and engaging the runner. The runner is slidably mounted on three guide members positioned symmetrically around the spindle and in parallel therewith. The guide members are parts of guiding profiled members forming part of the housing of the positioning apparatus. Special slide surfaces are arranged on the guide members. The housing of the positioning apparatus is manufactured through extrusion, preferably from a light material, such as aluminium, while the slide surfaces are made from a harder material.