nail down vs peg down

nail down and peg down both are verbs.

Word	Noun	Adjective	Verb	Adverb
nail down	No	No	Yes	No
peg down	No	No	Yes	No

As verbs, nail down and peg down are synonyms defined as:

Other synonyms of nail down include narrow, narrow down, pin down, specify.

nail down (verb)	peg down (verb)
make final; put the last touches on; put into final form	define clearly
define clearly	fasten or secure with a wooden pin
succeed in obtaining a position