A pipe wrench is any of several types of wrench that are designed to turn threaded pipe and pipe fittings for assembly (tightening) or disassembly (loosening). The Stillson wrench, or Stillson-pattern wrench, is the usual form of pipe wrench, especially in the US. The Stillson name is that of the original patent holder, who licensed the design to a number of manufacturers; the patent has since expired decades ago. A different type of wrench with compound leverage often used on pipes, the plumber wrench, is also called a "pipe wrench" in some places.