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.
A very good door stop can be easily made of a piece of metal as shown in the sketch. The metal is bent and fastened with screws to the wall against which the door swings. The extending end fits under the door knob and prevents it from striking the wall. - Contributed by C. R. Poole, Los Angeles, California.