A stilson wrench, like the [mousetrap], is one of those ingeniously simple inventions that is perfectly designed for a particular task and will never be improved upon. Invented by [machinist] [Daniel Chapman Stilson] (1826-1900) of [Durham], [New Hampshire], the stilson wrench has earned its place as the most popular type of [pipe wrench] used by [plumber]s and [pipefitter]s everywhere.

A stilson wrench works by pinching the [pipe] between two hardened, serrated jaws. The top jaw is connected to the handle by a loose sleeve, which allows the jaws to expand so the wrench can easily slip onto the pipe. [Torque] applied to the handle squeezes the jaws together. The more pressure that is applied, the tighter the wrench grips.

  Torque here
  pinches jaws
  together
   |
   v      ________________
         |  _   _________ |
---------| |-| |---,    | |
---------|_|-|_|-| |    | |
   Handle         | |    | |
                 | |    | |
                 |_|    |_|
                Lower    Upper
                 Jaw     Jaw

Stilson wrench (thing)