Spanner

A spanner is a hand tool used to apply torque to fasteners such as nuts and bolts. In British English and many other locales, the term spanner is standard; in the United States the same tool is typically called a wrench. The name derives from the tool’s function to span across the fastener and provide leverage for turning it.

Common types include open-ended spanners, box-end spanners, and combination spanners (one open-ended and one box-end). Socket wrenches use interchangeable sockets mounted on a ratcheting handle. An adjustable spanner, sometimes called a crescent wrench, has a movable jaw to fit various sizes. Hex keys (Allen wrenches) and Torx wrenches are used for hex- and star-shaped socket fasteners. Specialized forms include torque wrenches, which measure and control applied torque, and pipe wrenches, which grip round pipes.

Most spanners are made from steel alloys and finished with chrome plating or a satin polish to resist corrosion and wear. Adjustable spanners use a calibrated screw thread or a knurled knob to move the jaw. Quality spanners match standard sizing (metric or imperial) and have precise jaw faces to avoid rounding fasteners.

Spanners have a long history in mechanical engineering and are essential in automotive repair, plumbing, and construction. Their design emphasizes durability, fit, and ease of use. Proper selection of size, type, and torque rating is important to avoid damaging fasteners.