In this companion to American Levels and Their Makers, Vol. I, the author presents that great rarity a book on patents that both illustrates the patents (in a size large enough to be useful) and explains them. Two hundred and ten level patents are pictured and explained here, with explanations keyed to the patent drawings. They illustrate the major and continuing contributions by L.L. Davis, Justus Traut, the Stratton Bros., and L.S. Starrett, among others. To aid in identification, each patent is triply indexed: by date, patentee, and category (e.g., inclinometer, sighting level, adjustment mechanism, etc.). In addition, the book provides a brief history of the men who obtained the patents, information on whether, when, and how the patents were used, the progression of improvements in patent concepts over time, and information that may be useful in identifying mystery levels. This volume, relating patents to real tools, will prove an invaluable reference for tool collectors and dealers, as well as for students of industrial technology.