Abstract: Disclosed is a device for forming a hinge in a sheet of extruded plastic. Plastic material is extruded and passed between a pair of rolls to determine the thickness of the plastic sheet. A groove forming member of a scoring assembly then creates a groove in the sheet of plastic when the plastic is still warm. The groove forming process creates a plastic ridge on both sides of the groove. To flatten these ridges, the sheet then passes through a second set of rolls. The sheet of plastic, still warm, is then cooled by a conventional method. The scoring assembly is movable along the width of the sheet of plastic and is adjustable for the depth of groove. The scoring assembly can also be removable. Once a groove is created, the groove acts as a hinge and the sheet can be bent or folded along the grooved edge.