What is the significance of the graffiti in the Catcher in the Rye?

The opening scene is important because it takes place in a mental hospital and that questions the reader about how Holden got there and the events that leads to that. This book is in "bookend" structure- meaning that it begins and ends in the same place. (i think)

The closing scene is significant because the rain represents Holden starting over, or realising the sadness, and anger he kept with him. The carousel represents Holden's acceptance into the adult world.