The Saddle Square is a handy tool for transferring a layout line from one plane to an an angled plane surface to another . For example you can scribe around all four sides of a table leg, which allows you to scribe two perpendicular surfaces at a time. With 1-1/4" x 2-1/4" inside legs you can wrap a line around work pieces up to almost double its size. The most important issue is that it allows you to pick up on a line already scribed, and accurately transfer it to another face perpendicular to it. The Veritas Saddle Square is made of anodized aluminum, 2" wide, with both end faces machined square to within 1/4°.