The mounted assembly according to the invention comprises a framework 1 developing transversely to the direction of forward travel, provided with three points for attachment to the three point system of a towing vehicle, with an arm (3) in several articulated sections, provided at the lower end with an articulated head (4) for fastening a tool. The arm 3 and the head 4 are associated with driving means which ensure their displacement and hold them in position. The framework 1 is furthermore provided with means preventing the device from falling over backwards, these means consisting of a wheel 23 mounted on a deformable parallelogram 24 associated with a hydraulic thrust cylinder 25 coupled to control means which act on it so that the wheel 23 is always pressing on the ground when the assembly is moving over the latter.
