The commoners used longbows as a technology innovation that helped the English win many battles in the Hundred years war.
King John signed the Magna Carta saying that not even a monarch could take away a persons rights.
The Bunonic Plague got spread from rats that came from trading ships. Since lots of workers died from the plague, the workers who survived were able to demand a higher pay and rights.
The Hundred Years war contributed to the decline of feudalism by giving power from lords to monarchs and commoners. They did this because the monarchs collected taxes for their armies, so they didn't need the nobles to gather knights.