The Hough name comes from the Hough Company of Libertyville, Illinois, founded by engineer Frank G. Hough. In the late 1930s and 1940s, the company is credited with pioneering the self-propelled, rubber-tired wheel loader, sold under the trademark Pay Loader, at a time when most loading equipment relied on track-mounted or towed designs. This made Hough an early and influential name in the development of the modern wheel loader.

In 1952, the Hough Company merged into International Harvester, and its loader line continued under IH as the Pay Line series, including H-prefix models such as the H35, H60, and H90. These loaders were powered by Continental and International Harvester six-cylinder gasoline and diesel engines, reflecting the industrial equipment standards of the era.

Because Hough and its early Pay Line successors are older, less common machines, documentation on some specific models remains limited. The manuals available here focus on models such as the Pay Loader P600, covering engine service, transmission and gearbox repair, and general upkeep of the drivetrain and loader systems, along with the torque specifications and maintenance steps needed for careful, accurate work.

These manuals are aimed primarily at restorers and collectors preserving vintage construction equipment, along with independent shops and enthusiasts who occasionally service older industrial machinery. For anyone working to keep a Hough or early Pay Line loader running, the manuals provide practical, model-specific reference material that is otherwise difficult to find.