A pipe wrench is an adjustable wrench that is used, as the name implies, on pipes. Most often, pipe wrenches are used on threaded pipe, usually galvanized steel, black iron or similar metal pipes. A pipe wrench has two serrated jaws that are tightened and dig into the pipe for grip. The top serrated jaw adjusts up and down to fit different size pipes. The unique feature of a pipe wrench is that the teeth will only grip when turning the wrench in one direction (see above), so it almost acts as a ratchet wrench.