Adjustable wrench, also called a Stillson wrench, has serrated jaw surfaces to grip pipe and a movable jaw, at an slight angle to the fixed jaw, so that the angle increases the jaws' grip on the pipe, when it pivots slightly as force is exerted on the handle.
The pipe wrench, or Stillson® wrench is an adjustable wrench used for turning soft iron pipes and fittings with a rounded surface. The design of the adjustable jaw allows it to rock in the frame, such 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.
