monkey wrench

monkey wrench (plural monkey wrenches)

1. A wrench (spanner) with an adjustable jaw.
   • 1903, Shop Talk, Volumes 1-3, page 21,

     Did you ever stop to think whether or not you knew how a monkey wrench should be used?

   • 1948, George M. Warren, Simple Plumbing Repairs in the Home, Farmers' Bulletin, Issue 1460, page 2,

     With a monkey wrench on the hexagonal part of the stuffing box unscrew the stuffing box from the body of the faucet.

   • 2010, A. M. Murray, The Secret of the Serpent Mound, unnumbered page,

     There were two monkey wrenches for that, sitting in a bucket. Lisa held one wrench and I applied the other and in a few minutes we had removed the motor head and set it on the ground.

2. (idiomatic) An unexpected or troublesome problem, obstacle or dilemma.
   • 1926, New Outlook (volume 142, page 58)

     Professor Miller's careful research has thrown a monkey-wrench into the Einstein wheel, although it has far from discouraged the enthusiastic exponents of Einsteinism.

   • 2003, Robert D. Keppel, William J. Birnes, The Psychology of Serial Killer Investigations: The Grisly Business Unit, page 130,

     Meanwhile the killer, either knowing for sure or by instinct that the police have incorrectly profiled him, throws monkey wrenches into the task force investigation by changing his modus operandi (MO) for no other reason than to trick the police.

   • 2005, Julia E. Richards, R. Scott Hawley, Catherine A. Mori, The Human Genome: A User's Guide, page 159,

     It has been suggested that myocilin missense mutations that cause severe disease are monkey wrenches, causing disease through actively causing a problem rather than through a lack of the gene product or function.

   • 2007, Carol Hoenig, The Author's Guide to Planning Book Events, page 59,

     Therefore, even if the author is a celebrity, something may throw a monkey wrench in an event's success.

     It is here where I must mention the monkey wrench that dramatically hurt events I scheduled during the period of 1996–2001.

   • 2009, Ken Reamy, The Balaam Surrogate, page 210,

     Girard had programmed some electronic "monkey wrenches" into the control panel that with the stroke of a key, would render the device inoperable.

Some writers distinguish on functional grounds between 'traditional' adjustable wrenches designed for turning nuts (and which have flat-sided jaws) and others, sometimes called pipe wrenches or Stillson wrenches, designed for gripping and turning pipes (which may have curved, serrated jaws). The term monkey wrench may refer to either.

• gas grips (UK)
• (wrench with adjustable jaw): adjustable spanner (UK, Australia), pipe wrench (with serrated jaws)

• monkey-wrencher
• throw a monkey wrench in the works

• throw a spanner in the works (UK, Australia)