Since people frequently needed length measures for everyday activities, American companies realized in the late 19th century that rulers could be effective giveaways for promoting their businesses. Some of these were based on a design patented by Henry Adler, an inventor who manufactured iron and sheet metal products in Pittsburgh, so this page also includes three of the four patent models for scale rules found in the mathematics collections. (The fourth is shown on the page for triangular rules.) Since the promotional rules and patent models were often combination instruments—putting length measures together with paper cutters, protractors, and the like—these objects are included in this category.
