board rule vs measuring rod

board rule and measuring rod both are nouns.

Word	Noun	Adjective	Verb	Adverb
board rule	Yes	No	No	No
measuring rod	Yes	No	No	No

As nouns, measuring rod is a hypernym of board rule; that is, measuring rod is a word with a broader meaning than board rule:

board rule: a measure used in computing board feet
measuring rod: measuring instrument having a sequence of marks at regular intervals; used as a reference in making measurements

Other hypernyms of board rule include measure, measuring stick.

board rule (noun)	measuring rod (noun)
a measure used in computing board feet	measuring instrument having a sequence of marks at regular intervals; used as a reference in making measurements