fastener vs fixing

fastener and fixing both are nouns.

Word	Noun	Adjective	Verb	Adverb
fastener	Yes	No	No	No
fixing	Yes	No	No	No

As nouns, fastener and fixing are synonyms defined as:

fastener and fixing: restraint that attaches to something or holds something in place

Other synonyms of fastener include fastening, holdfast.

fastener (noun)	fixing (noun)
restraint that attaches to something or holds something in place	the act of putting something in working order again
a person who fastens or makes fast	the sterilization of an animal
	(histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body
	restraint that attaches to something or holds something in place