"plucked blades of grass"

This action performed by Hassan is an example of imagery where it illustrates that idea that Hassan has no use in the activity of reading. While Amir gets ready to read, Hassan can only sit out of boredom because of the social issue pertaining to education and illiteracy. It is due to Hassan ethnicity that he can only be a servant and cannot have an education. Therefore, Hassan is only able to listen when Amir starts to read.