flathead

Flathead is a term used for several unrelated concepts in hardware, engineering, biology, and anthropology. The intended meaning depends on context.

In hardware, a flathead refers to a flat, single-slot screw and the corresponding screwdriver blade. The term describes the slotted head that sits flush with the surface. Flathead screws are common in older devices and early automobiles, but less common in modern fasteners, which often use Phillips or Torx drives.

In automotive engineering, a flathead engine is a side-valve design with a flat cylinder head. Valves sit beside the cylinder instead of in the head. The famous Ford flathead V8 is an example. Flathead engines are simple and cheap to produce but generally produce less power and efficiency than overhead-valve designs.

In biology, the flathead catfish (Pylodictis olivaris) is a large freshwater fish native to parts of North America. It has a broad, flat head and a scaleless body. It is a bottom-dweller and can reach substantial sizes; in some areas it is considered both a sport fish and an ecological concern when introduced.

Historically, Flathead was used by European settlers to refer to certain Salish-speaking peoples of western Montana, including the Pend d’Oreille and Kootenai. The term appears in the name Flathead Reservation and is part of the broader identity of the Confederated Salish and Kootenai Tribes today.