the slide 6 is guided on a substructure 3 and can move in and against the direction of travel 4 the substructure 3 is made up of two parallel guide rails 5 at a distance from each other engaging with front and rear cross beams 28 a 28 b at the ends on the front cross beam 28 a a hydraulic cylinder 9 is fastened as motor operated drive unit 7 with its piston rod 9 a projecting to the rear and connected to the end of the slide 6 when the piston rod 9 a travels the slide 6 and thus also the fifth wheel 2 is moved laterally by the same amount fig5 shows a top view of the slider where the arrangement of the hydraulic cylinder 9 on the boxlike substructure 3 is especially conspicuous in order to relieve the strain on the hydraulic cylinder 9 during driving locking means are present on the guide rails 5 and the slide 6 by which a removable positive connection can be produced between slide 6 and substructure 3 on the part of the guide rails 5 this is a toothing 29 which can be formed on the inner facing sides of the guide rails 5 in the bottom view of fig6 oppositely situated clamping shoes 14 are provided on the slide.