Sentence:  "Drawing materials," he thought, "I used to love drawing as a lad. I can afford some plain paper and pencils, surely? And a <WSD>rubber</WSD>, too." He smiled at the memory of an elderly uncle, also fond of drawing, who′d always called <WSD>rubbers</WSD> ‘lead eaters'. 
Meaning of the word marked with <WSD> tags:  An eraser.