Abstract: This tracing device adapted to be mounted to the front end of a tractor comprises a lateral jib having a length equal to the width of the lanes on which an agricultural or similar product is to be spread or sprayed. This jib is pivoted about a vertical pintle carried by a framework fixed to the front of the tractor. The outer end of the jib is provided with a jib-supporting and tracing wheel. Alternatively, the jib may be either telescopic or made of two hingedly interconnected frames, with a pair of wheels supporting the hinge and the tracing wheel located at the outer end of the outer frame. A rope attached to the tractor and to the outer end of the jib is provided for constantly keeping the jib on one or the other side of the tractor so as to form with the latter an angle of 90.degree..