A marking gage is used to mark off guidelines parallel to an edge, end , or surface of a piece of wood or metal. It has a sharp spur or pin that does the marking.
Marking gages are made of wood or steel. They consist of a graduated beam about 8 inches long on which a head slides. The head can be fastened at any point on the beam by means of a thumbscrew. The thumbscrew presses a brass shoe tightly against the beam and locks it firmly in position. The steel pin or spur that does the marking projects from the beam about 1/16 inch.
To draw a line parallel to an edge with a marking gage, first determine the distance the line must be from the edge of the stock. Adjust the marking gage by setting the head the desired distance from the spur. Although the bar of a marking gage is graduated in inches, the spur may work loose or bend. If this occurs , accurate measurement should be made with a rule between the head and spur. To draw a line after setting the gage, grasp the head of the gage with the palm and fingers ; extend the thumb along the beam towards the spur. Press the head firmly against the edge of the work to be marked, and with a wrist motion tip the gage forward until the spur touches the work. Push the gage along the edge to mark the work , keeping the head firmly against the edge of the work.