Abstract: The invention is an extendable compartment apparatus installed in a vehicle in such a manner that a platform can be cantilevered out from the vehicle body on an interlocking rail and bearing system. The apparatus includes a glidable platform, channel section stationary rails and angle section glidable rails. The glidable rails move along bearings which are located at the outermost end of the stationary rails and at the innermost end of the glidable rails, respectively. The glidable rails are limited in their movement such that they remain within the stationary structure along approximately one-third of their length. The platform can be mechanized using a DC motor and a rack-and-pinion gear system or worm gear. Finally, the glidable platform can be enclosed using side walls, a back wall, and a roof and thereby made weatherproof for use in combination with a camper vehicle.