Sentence:  And the bed that sagged in a certain place where all the weight had been put too many times before and the walls fine and <WSD>thin</WSD> for overhearing talk in the next room when Gratt went out for ice , the sound coming through the walls like something on the other side of the curtain , so you knew they heard you when they were quiet and while you lay wondering what they had heard you listened . 
Meaning of the word marked with <WSD> tags:  of relatively small extent from one surface to the opposite or in cross section