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.
Procure an ordinary packing box and mark a line from corner to corner on both ends, as shown, from A to B in Fig. 1. Pull out all the nails from the corners that may cross the line. Nail the top to the box and saw it on the lines marked and two shelves will
Fig 1 FIG.2 Two Shelves Made of One Box
be formed which may be used as shown in Fig. 2. Boxes dovetailed at the corners will make excellent shelves and look neat if painted.