Photo: Courtesy of Wikipedia
What is a Monkey Wrench?
A monkey wrench is a tool with two parallel, smooth-face jaws. The upper jaw is fixed while the lower jaw is connected to an adjustable screw mechanism that can create wider or narrower openings. Monkey wrenches were commonly used in carriage making and excel at gripping the parallel edges of 4-, 6- and 8-sided nuts and bolts
While it resembles a pipe wrench it’s NOT a pipe wrench. The jaws of a pipe wrench contain ridges for better gripping smooth surfaces and round surfaces, and are slightly angled so they pinch the pipe tighter when pressure is applied to the handle.