Check the listing for details. Beam Compass Trammel Points- circle arc drawing layout tool for pencils sharpie. Condition: New. Listed at 17.49 USD. These trammel points are designed to draw and measure large diameter arcs and circles. Clamp the points onto a rigid beam and adjust the distance between the points to determine your arc radius. They work just like a compass but at any size you need. Included in each set:2 trammel points with nonmarring tightening thumbscrews2 sharpened steel points, 3.5 inches long Specifications:Smallest possible circle radius: 1 inchLargest possible circle radius: infinite!Compatible with pens, pencils, carpenter's pencils, sharpies, nails, screws, and more. Any writing tool up to 0.51 inches in diameter will fit inside the body, giving you way better writing tool options than competitors.Clamps onto any rigid beam up to 1.54 inches thick. Can be clamped directly onto 2x4 (or 2x6, 2x8, etc) construction lumber.Manufactured by Wise Oak Design in the USA