Abstract: A gage for marking a cutting line across the lower end portion of a door to facilitate cutting of the door to the proper length to clear carpeting, a threshold or the like. The gage includes an elongated rod which adjustably supports fixturing members having hinge curls adapted to interleave with the curls of the hinge wings on the door jamb and adapted to be attached to the wings by hinge pins. Once the rod has been fixtured, an elongated marking guide on the lower end portion of the rod is adjusted vertically and angularly to a position in which the lower edge of the guide just clears the floor or threshold when the guide is swung about the axis of the rod. After the guide has been locked in its properly adjusted position on the rod, the gage is detached from the door jamb and is placed on the door with the curls of the fixturing members in alinement with curls on the hinge wings of the door.