From the preface:
The steel square is the carpenter's handbook, instructor, and tool without price. ... This book on the steel square tells the carpenter "how to do it." It explains clearly, by means of illustrations and detailed instructions, the various markings which appear on the square, and the purposes for which they are used by the carpenter in the course of his daily work. Instruction is also given on the use of the square in the construction of the different parts of wood-framed buildings, including detailed information on the building of roofs. The laying out of the various cuts is illustrated in a step-by-step fashion which makes some of the most difficult operations seem easy.