Headless set screws have been around for a long time, with the straight slot being the oldest drive type (due to its ease of machining ), but the demand for headless set screws experienced a marked increase in the first and second decades of the 20th century, when a penchant for better industrial safety, a campaign with the slogan "safety first",  swept the industrialized nations of North America and Europe as a part of the larger Progressive Movement . This surge in safety consciousness was a backlash against the often-atrocious industrial safety standards of the era. Hallowell, Sr., a . industrialist whose corporation was one of several that pioneered the commercialization of the hex socket drive, noted in his memoir that line shafting , which was ubiquitous in the industrial practice of the time, often had headed set screws (with external-wrenching square drive ) holding the many pulleys to the line shafts, and collars holding the shafts from axial movement. Gear trains of exposed gears were also common at the time, and those, too, often used headed set screws, holding the gears to the shafts. His company's chief products at the time were shaft hangers and shaft collars of pressed-steel construction. The "safety craze" created a burgeoning demand for headless set screws on pulleys, gears, and collars to replace the headed ones, so that workers' clothing and fingers were less likely to catch on the exposed rotating screw head. It was this heightened demand that prompted Hallowell's firm to get into the screw-making business and to explore socket-head drive designs. With . Robertson holding fresh patent rights on a practical-to-make square-socket drive, the firm soon pursued the hex socket drive.