Sentence:  Now hollow out the inside of the boat with a <WSD>gouge</WSD> or <WSD>gouges</WSD>. ("Firmer" <WSD>gouges</WSD>, ground on the outside of the curve, are used. "Paring" <WSD>gouges</WSD> are useless.) 
Meaning of the word marked with <WSD> tags:  A chisel with a curved blade for cutting or scooping channels, grooves, or holes in wood, stone, etc.