Sentence:  At the same time he watched carefully to see how one attached pegboards to stone <WSD>walls</WSD> , but Mr. Blatz was usually standing in his line of vision and it all seemed so simple that he did n't like to disclose his ignorance . 
Meaning of the word marked with <WSD> tags:  an architectural partition with a height and length greater than its thickness; used to divide or enclose an area or to support another structure