A pneumatically powered test fixture for bracing, holding and/or handling solid, bulky objects such as gas meters or the like. The fixture readily permits service or repairs and renders meters readily accessible and easily maneuverable. A rigid frame is adapted to be secured to a stable workbench or support, and an optional support plate may couple the frame to the support surface. A rigid mounting spacer secured to the frame mounts a pneumatically powered trunnion. When an optional frame mounting plate is omitted, the trunnion mounting spacer will be affixed directly to the workbench. A rigid, U-shaped cradle captivates a meter to be repaired or serviced. The cradle is rotatably suspended above the supporting surface by the trunnion, and the cradle can be manually rotated into a variety of user-selectable positions to readily expose all structural portions of the meter. A pneumatic cylinder mounted at the top of the cradle engages a meter in response to pressurization independently of meter width or configuration. Thus operator adjustments ordinarily are not required to assimilate meters of varying dimensions and configurations. The trunnion, which rotatably mounts the cradle to the frame, includes an internal forcing cone which locks the trunnion shaft in response to axial displacement. Trunnion activation restrains the cradle in a given radial orientation. The trunnion assembly comprises an internal, cylindrical bearing member coupled to the cradle for enabling relative rotation. A pair of generally semi-circular disc retainer members internally disposed within the trunnion prevent permanent lock up, and enable manual cradle rotation after pneumatic trunnion release.