The pipe wrench, or Stillson® wrench is an adjustable wrench used for turning pipes or other items with a rounded surface. The design of the adjustable jaw is such that any forward pressure on the handle tends to force the jaws tighter together.
The U.S. Patent Office issued to Daniel C. Stillson on September 17, 1870, for this basic design as an "improved monkey wrench".
The image below and right is of a pipe wrench designed for use in space restricted areas.