Practical plane and solid geometry for advanced students, including graphic statics, adapted to the requirements of the South Kensington syllabus (1899)
Harrison, Joseph, Baxandall, George Albert · London Macmillan · leaf 212
VIII FUNDAMENTAL RULES OF PROJECTION 197 … at right angles to the auxiliary plane, or either hinge may be unfastenedfor the purpose of rabatment. Theorems 1 and 2 apply to any object, conceived as anassemblage of points. They may be put in the form ofrules. Thus suppose the plan and elevation on xy to havebeen drawn ; then Rule 1. — To…