BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective, diagrammatic view of a roller of the invention located with respect to a coacting roller, and a railroad tie to be incised is shown passing between the rollers; FIG. 2 is a broken-away, exploded view of a portion of the roller of FIG. 1, some of the teeth being removed for purposes of clarity; FIG. 3 is a broken-away, perspective view of a