The monkey wrench is a type of adjustable wrench, a 19th century American refinement of 18th-century English coach wrenches. It was widely used in the 19th and early 20th century. It is of interest as an antique among tool collectors and is still occasionally used in maintenance and repair when it happens to be convenient. The term monkey wrench is also sometimes used loosely, usually by non-tradesman, to refer to the pipe wrench (owing to their broadly similar shapes).