Free Rocker Box Plans Courtesy of The U.S. Bureau of Mines - Gold Mining Prospector's Rocker Box

Here is another fine PDF courtesy of E. D. Gardener and C. H. Johnson. It was published by the US
Bureau of Mines in September, 1934 Includes two very clear pages of diagrams. The rocker box itself is shown in a portrait style and reads better in landscape, but you can print it and read it easily then without cracking your neck.
http://kf6bxh.com/rocker.html