The Linchpin Theory expounds the existence of certain unpredictable and non-repeating incidents defined as X-Events. John Casti on his book X-Events: Complexity Overload and the Collapse of Everything proposed this theory that each individual event if failed can lead to a domino effect with catastrophic implications.
The trailer hitch fits in the middle of a yoke end that is attached to a hydraulic arm; a hitch pin threads through the yoke end and the trailer hitch to connect them, and the lynch pin secures into the hole at the end of the hitch pin to lock it in place.


