Abstract: A positioning apparatus for supporting and guiding a tool to effectuate a work function on a predetermined area of a stationary surface. The apparatus comprises a support guide frame which is displaceably connected to a displaceable base. The base is displaceable and positioned to a stationary location relative to the predetermined area. The support guide frame has a pair of spaced-apart side arms each connected at a rear end thereof to the base by a respective pivotal telescopic coupling. The telescopic coupling permits each side arm to be indendently displaced axially and pivotally to one another in parallel vertical planes. A transverse guide beam is secured to the side arms and is axially displaceable relative thereto. A tool carriage is secured to the guide beam and controllably displaced therealong. The carriage has a telescopic support member axially displaceable in a vertically pivotal bushing.