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.
Construct a box of pasteboard or thin wood, about 9 in. long, 3 in. wide and 2 in. thick, and fasten two pieces of mirror in the ends at an angle of 45 deg., both sloping in the same direction with their reflecting surfaces toward each other. An opening as large as the mirror is cut, facing it, in the box at the end A, and a small hole bored through at the end B so that it will center the mirror. Both of these apertures are covered with plain pieces of glass.
Ill: The Reflecting Device as It is Used in a Car Window for Viewing the Scenery Ahead
In use, the end A is placed outside of the car window and the user places an eye to the small hole B. It is impossible to be struck in the eye with a cinder or flying object. - Contributed by Mildred E. Thomas, Gordon, Can.