Both ends of both rules have irregularly-shaped aluminum mounts that may be screwed to a drafting machine. A green cardboard box for the shorter rule is marked at one end: K+E PARAGON (/) DRAFT. MACH.

Vard Beecher Wallace (1901–1988) of Sierra Madre, Calif., applied for a patent for these attachments in 1939 and received it the next year. He and a partner, Paul H. Ford, operated Vard Mechanical ...