nut and bolt vs fixing

nut and bolt and fixing both are nouns.

Word	Noun	Adjective	Verb	Adverb
nut and bolt	Yes	No	No	No
fixing	Yes	No	No	No

As nouns, fixing is a hypernym of nut and bolt; that is, fixing is a word with a broader meaning than nut and bolt:

Other hypernyms of nut and bolt include fastener, fastening, holdfast.

nut and bolt (noun)	fixing (noun)
a fastener made by screwing a nut onto a threaded bolt	the act of putting something in working order again
	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