Monkey wrench

A tool which is similar to a pipe wrench. While a pipe wrench has teeth and a loosly mounted head that allows it to "bite" into the pipe and tighten as a strain is put on the handle, a monkey wrench has adjustable, smooth jaws that always remain parallel. The money wrench is used for turning pipe unions, the heads of bolts, and other flat surfaced object. The monkey wrench has pretty much been replaced by the Cresent wrench and other more modern adjustable wrenches. Monkey wrenches are still used on old steam engines (not necessarily locomotives) and boiler fittings. Some call it a "steamboat" wrench. (definition submitted by George King III). The expression "throw a monkey wrench" into something generally means to sabotage something or to cause a problem or delay in performing repairs. See also left-handed monkey wrench