Abstract: A molding device for placement of formed cementitious material such as concrete on a mounting surface. The device is used in combination with a supply of pressurized cementitious material communicated through a hose from a conventional cement pump or the like. It features a mold unit having an a compression chamber at a first end communicating with an extrusion chamber at a second end. Cement material is forced into the compression chambers from the cement pump and extruded from the exit orifice of the extrusion chamber. The device is propelled forward by the pressure from the injected cement against the front of the device and away from the formed material means control any upward travel of said mold unit caused by said internal pressure against said top wall. Weights may be added to the top of the device to limit upward travel and a steering mechanism may be added to the front of the device to steer it on a defined course.