Linchpin
A linchpin, also spelled linch pin, lynchpin, or lynch pin, is a fastener used to prevent a wheel or other part from sliding off the axle upon which it is riding. The word is first attested in the late fourteenth century and derives from Middle English elements meaning "axletree pin".Securing implements onto the three-point hitch of a tractor is an example of application.  Linchpins may also be used in place of an R-clip for securing hitch pins.

Metaphorical use
The word "linchpin" is also used figuratively to mean "something [or someone] that holds the various elements of a complicated structure together".

See also
Circle cotter – Ring type of retaining component
Circlip – Type of fastener or retaining ring
Cotter (pin) – Pin or wedge passing through a hole to fix parts tightly together
Hairpin clip – reusable type of formed wire used on a grooved shaft, designed to be easily installed and uninstalledPages displaying wikidata descriptions as a fallback
Kingpin (automotive part) – Main pivot in a vehicle's steering mechanism, or part of the fifth wheel coupling for a semi truck
R-clip – Type of fastener made of a springy material
Split pin – Metal fastener with two tines that are bent during installation
Spring pin – Mechanical fastener that secures the position of two or more parts relative to each other

References


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