The increased trend in airplane design toward metal construction has focused the attention of airplane designers upon many new problems. Chief among these problems is that of metal-wing construction and, in particular, metal-spar design. In general, the methods used in wood-spar design are adaptable to the constant depth, continuous web metal spar. With respect to trussed metal spars, however, the methods of design have been quite arbitrary. This report may be considered to be roughly divided into three parts, namely: (1) Discussion and outline of preliminary design; (2) Theory, development, and outline of precise design or analysis; and (3) Illustrative examples and proof of precise methods.