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 writing desk for a child can be easily made as shown in the sketch. The materials necessary are a board of suitable size, two screwhooks, four screweyes and a pair of rods for braces. The hooks are screwed into the back of a chair and the screweyes into the board, as shown. This desk is instantly attached or taken down when desired. If the chair is light and apt to tip over, make the rods long enough to reach to the floor. - Contributed by John V. Loeffler, Evansville, Ind.
Ill: The Writing Board is Easily Attached to, or Detached from, an Ordinary Chair Back