Abstract: A device for adjusting the working width of a road finisher, comprises a main support beam which is adapted to be carried by the road finisher behind the device for finishing the road surface. The main support beam includes a central plate portion having a pair of tubes secured to each side thereof which extend laterally of the road finisher. An adjustment beam for carrying a ground support for the finisher includes a rod portion extending into each tube and a respective interior and exterior side wall at the respective ends of the adjustment beam. The rod portions are movable in each tube and they are secured on the portion extending exteriorly of the tube to the exterior side wall. The rods are guided within the tube by guide means which bear between the rod and the tube. In addition, the exterior of the adjustment member is guided by second guide means which support the adjustment beam on the exterior of the tubes.