Accurately Marks and Finds the Center Line, works for wood up to 3.5 inches. Marking Center Finder is Perfect for determining exact centers on the edges of boards. when making biscuit slot cuts, drilling dowel joints,for assembly work and more. Easy to USE:Just insert the pencil into center of jig and make your mark. Gauge Woodworking Scriber Woodworking Tools Please see my other items. If you buy several items you get discounts.