Sentence:  Jeff was bent low over the backboard, working with the <WSD>knife</WSD>, a steady sawing motion, his shirt soaked through with sweat. 
Meaning of the word marked with <WSD> tags:  A utensil or a tool designed for cutting, consisting of a flat piece of hard material, usually steel or other metal (the blade), usually sharpened on one edge, attached to a handle. The blade may be pointed for piercing.