A pipe wrench is an adjustable wrench used for grasping and turning soft iron pipes and other fittings that have a rounded surface. A pipe wrench, also known as Stillson wrench, has a solid housing and hardened steel jaws which provide excellent bite and grip.
The adjustable jaw of a pipe wrench is designed to rock in its frame so that any forward pressure on the handle tends to pull the jaws tighter together. Teeth angled in the direction of turn dig into the soft pipe.
Pipe wrenches are usually sold in the following sizes: 10", 14", 18", 24", 36", and 48". (A 10" or 12" model will handle most household repair jobs.) They are usually made of steel or aluminum. Teeth, and jaw kits (which also contain adjustment rings and springs) can be bought to repair broken wrenches, as this is cheaper than buying a new wrench.
Also see chain pipe wrench.