Monkey wrench

The monkey wrench is an adjustable wrench

Wrench

A wrench or spanner is a tool used to provide a mechanical advantage in applying torque to turn bolts, nuts or other items designed to interface with a wrench....

 (spanner in British English

British English

British English, or UK English or English English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

) that was popular in the nineteenth century but is rarely used today. Its use has generally been replaced by the adjustable-end wrench

Adjustable spanner

An adjustable spanner, shifting spanner, shifter, fit-all, crescent wrench or adjustable-angle head wrench is a tool which can be used to loosen or tighten a nut or bolt. It has a "jaw" which is of adjustable size, which allows for different size nuts and bolts to be handled by the same spanner...

, which has a compact head and so is more easily used in confined places.

The term "monkey wrench" is also used colloquially (and inaccurately) to refer to the pipe wrench

Pipe wrench

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...

.

Concerning the origin of its name, this story has been repeated in several publications in the late nineteenth and early twentieth centuries:

That handy tool, the "monkey-wrench", is not so named because it is a handy thing to monkey with, or for any kindred reason.

The monkey wrench is an adjustable wrench

Wrench

A wrench or spanner is a tool used to provide a mechanical advantage in applying torque to turn bolts, nuts or other items designed to interface with a wrench....

 (spanner in British English

British English

British English, or UK English or English English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

) that was popular in the nineteenth century but is rarely used today. Its use has generally been replaced by the adjustable-end wrench

Adjustable spanner

An adjustable spanner, shifting spanner, shifter, fit-all, crescent wrench or adjustable-angle head wrench is a tool which can be used to loosen or tighten a nut or bolt. It has a "jaw" which is of adjustable size, which allows for different size nuts and bolts to be handled by the same spanner...

, which has a compact head and so is more easily used in confined places.

The term "monkey wrench" is also used colloquially (and inaccurately) to refer to the pipe wrench

Pipe wrench

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...

.

Etymology

Concerning the origin of its name, this story has been repeated in several publications in the late nineteenth and early twentieth centuries:

That handy tool, the "monkey-wrench", is not so named because it is a handy thing to monkey with, or for any kindred reason. "Monkey" is not its name at all, but "Moncky." Charles Moncky, the inventor of it, sold his patent for $2000, and invested the money in a house in Williamsburg, Kings County, where he now lives.

In his interesting article upon the genesis of machine design, Mr. W.H. Sargent spoke of the slide which moves up and down in the handle of a monkey wrench as resembling a toy monkey, and thereby drew an analogy. To this Mr. H.E. Madden writes: "The wrench is not named from this, neither is it so called because it is a handy thing to 'monkey' with. The right name is 'Moncky.' Charles Moncky, the inventor of it, sold his patent for $2,000, and invested the money in a house in Williamsburg, Kings County, N.Y., where he afterward lived.

However, this story has been refuted by historians, and there is evidence that screw-adjustable wrenches and even the term monkey wrench were used long before, at least from about 1840.