Sentence:  He went down to Mills and Bradley 's Hardware Store and bought a full set of carpenter 's tools , including a rotary power saw and several other pieces of power machinery that Mr. Mills said <WSD>were</WSD> essential for babbiting and doweling , whatever they were . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)