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.
In mechanical drawings cast iron is indicated by a series of straight lines across the parts made of this material. These lines can be quickly made with the usually discarded pencil stubs, if these are saved and sharpened i n the following manner: The point is filed flat, as shown at A; then a slot is filed in the center of the lead with a knife file, as shown at B, and the points sharpened as in C. In this way two lines are drawn at one stroke neatly and in half the time. - Contributed by J. Kolar, Maywood, Ill.