fastener vs holdfast

fastener and holdfast both are nouns.

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

As nouns, fastener and holdfast are synonyms defined as:

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

Other synonyms of fastener include fastening, fixing.

fastener (noun)	holdfast (noun)
restraint that attaches to something or holds something in place	restraint that attaches to something or holds something in place
a person who fastens or makes fast