A new teacher shows up at the school and asks to borrow an eraser. The teacher is using an old one that's been in his pencil case for a long time, so it's safe to assume that she's trying to erase something with the new one. The new teacher doesn't seem to understand that the old one has been in use for so long, and that she can't possibly be using a new one to erase a tiny part of a word. The old one, on the other hand, has been using it for years, and he's sure that the new teacher isn't going to be using it to erase anything. He's going to take the eraser from the teacher's pencil case and try to erase the little bit of the word that she wants to erase.