Donald A. Hall Sr. Professional Triangular Drafting Scale Ruler (Circa 1925)

A professional architectural and engineering triangular boxwood drafting scale ruler used for aircraft structural design. — Donald A. Hall Sr. Professional Triangular Drafting Scale Ruler (Circa 1925) · Donald A. Hall Estate Collection

Preserved from Donald A. Hall Sr.'s drafting table, this professional triangular drafting scale ruler was utilized during his mid-1920s engineering tenures at Douglas Aircraft, the Ford/Stout Metal Airplane Division, and Ryan Airlines. Featuring engraved proportional ratios along its three faceted edges, this precision instrument was used to draw scale general arrangements, fuselage bulkheads, and wing structural assemblies for landmark aircraft including the Douglas World Cruiser and the Ryan NYP.