Sentence:  He also bought a huge square of pegboard for hanging up his tools , and lumber for his workbench , sandpaper and glue and assorted nails , levels and T squares and plumb lines and several gadgets that he had no idea how to use or what they <WSD>were</WSD> for . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)