Invented by a practicing architect, the AlumiDrafter engineers scale ruler provides the user all the advantages of a traditional triangular scale in addition to many other features, while solving the portability problem of its bulkier counterpart. Four tools in one! Measure and scale drawings, draw circles and arcs, draw angles and triangles, or use as a cutting edge. Standard engineer graduations include: 10, 20, 30, 40, 50, 60. Great tool for professional engineers, engineering students, drafters.