back saw vs hand saw

back saw and hand saw both are nouns.

Word	Noun	Adjective	Verb	Adverb
back saw	Yes	No	No	No
hand saw	Yes	No	No	No

As nouns, hand saw is a hypernym of back saw; that is, hand saw is a word with a broader meaning than back saw:

back saw: a handsaw that is stiffened by metal reinforcement along the upper edge
hand saw: a saw used with one hand for cutting wood

Other hypernyms of back saw include carpenter's saw, handsaw.

back saw (noun)	hand saw (noun)
a handsaw that is stiffened by metal reinforcement along the upper edge	a saw used with one hand for cutting wood