This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Anyone who has used a file knows what skill is required to produce flat surfaces. A fixture which is nothing more than a mirror properly placed enables the operator to sight along the file and see at all times just how the file is running. - Contributed by A. F. Stearns, Madison, Wis.
Ill: The File can be Seen in the Mirror and Its Direction Controlled for Filing Flat Surfaces