Since 1869, Crescent Lufkin has stood at the forefront of measuring tools and equipment, with industry-leading quality and innovation. We enable the consumer or professional user with reliable, precise, durable lines of products, including our wooden measuring rules. Since patenting the Lufkin Folding Rule in 1919, we've been manufacturing top-quality tools, like this rule which features brass joints, clear graduation markings on both sides and edges, and two extending slide rules.From the ManufacturerCoopertools X48 8-Inch x 5/8-Inch Wood Spring-Joint Extendable Folding Ruler with graduated slide that extends up to full 6'. Slide runs under friction in T-slot and has a stop at each end so slide will not fall out. Marked both sides and both edges to 1/16ths of an inch, 16" stud centers in red, regular outside markings. Numbering begins on inside of rule; measurement lies close to the work. To take an inside measurement; open rule to within 6" or less of the distance. Butt square end against one side of opening. Extend slide until it strikes other side. Add measurement on slide to that shown at other end of rule for an exact measure of the opening.