Skid-steer 320D loader with bucket attachment.

Skid-steer loaders are typically four-wheel vehicles with the wheels mechanically locked in synchronization on each side, and where the left-side drive wheels can be driven independently of the right-side drive wheels. The wheels typically have no separate steering mechanism and hold a fixed straight alignment on the body of the machine. Turning is accomplished by differential steering, in which the left and right wheel pairs are operated at different speeds, and the machine turns by skidding or dragging its fixed-orientation wheels across the ground. Louis Keller, of Edgeley, ND, and his brother, Cyril, invented the skid-steer loader, which in 1958 was bought by the Melroe Manufacturing Co., Gwinner, ND, which would later become the Bobcat Co.