This section is from the book "Modern Shop Practice", by Howard Monroe Raymond. Also available from Amazon: Modern Shop Practice.
The marking gage is used for drawing a line at a given distance from, and parallel to, the already trued and jointed surface or edge of a board or piece of wood that is being marked to dimensions. There are many forms of this tool, but in the "Improved Marking Gage," illustrated in Fig. 56, the head is reversible. The flat side of the head is used for ordinary straight work, while the reverse side, having the brass face with two projecting ribs, enables the operator to run a gage line with perfect steadiness and accuracy around curves of any radius, either convex or concave - a feature much to be desired in a pattern-maker's gage.
Fig. 56.
 
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