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 , <WSD>levels</WSD> and T squares and plumb lines and several gadgets that he had no idea how to use or what they were for . 
Meaning of the word marked with <WSD> tags:  indicator that establishes the horizontal when a bubble is centered in a tube of liquid