The Trammel Point/Edge Parallel Marker Kit is a dual purpose tool for circular and angular layout as well as drawing border lines which follow the contour of a slab. Install the plastic edge guide and a pencil holder to trace the contour of the slab edge. As a trammel point kit, it acts just like a compass for paper (just a much larger scale.) You will use this tool to find perfect angles, straight lines, and trace perfect circles for layout and design. You can add additional connecting tubes to extend the radius of this tool.