sheath knife vs case knife

sheath knife and case knife both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheath knife	Yes	No	No	No
case knife	Yes	No	No	No

As nouns, sheath knife and case knife are synonyms defined as:

sheath knife and case knife: a knife with a fixed blade that is carried in a sheath

sheath knife (noun)	case knife (noun)
a knife with a fixed blade that is carried in a sheath	a knife with a fixed blade that is carried in a sheath
	a metal blade with a handle; used as cutlery