perpendicular to the line gl which is perpendicular to the slope face f and passes through the center of gravity g of the paving machine m the main body of the anchor vehicle b has independently steerable crawlers 103 and a main frame 101 mounted on the crawlers a driver 39 s cab 102 a wire feeding apparatus a hydraulic pressure generator and other components are mounted on the frame 101 the wire feeding apparatus includes a winch 109 which feeds out or takes up the wire a pair of arms 107 which are spaced apart and are pivotally mounted on fulcrums 120 guide sheaves 104 which are rotatably mounted on the arms 107 guide sheaves 105 which are rotatably attached to the fulcrums 120 and hydraulic piston cylinder units 110 which are operable to adjust the angles and heights of the arms 107 the wires w from the winch 109 are wound around the guide sheaves 104 and 105 and they are connected to the paving machine m the arms 107 guide sheaves 104 and units 110 provide a height adjusting means as shown in fig6 the swinging ends of the arms 107 are connected together by a member 106 therefore only one hydraulic cylinder unit is required to move both arms synchronously and only one winch 109 is provided a light receiving device 131 which receives the laser beam can be a conventional photosensitive cell which is attached at or near the center of the member 106 as shown in fig5 the light receiving angle of the device 131 can be adjusted in order to receive the laser beam l at a right angle in lieu of a single diode photosensitive device it is.