One of the most important literary devices used in The Scarlet Letter is symbolism. The novel opens with the image of a rose at the door of the prison where Hester is being held. The symbolism of the rose -- a thing of beauty and something to be prized -- next to the prison establishes a central theme of the novel: The goodness of Hester in contrast to her sin and the communities treatment of her because of her sin. The Letter A is also an obvious symbol of Hester's sin as it is the literal representation of her sin and punishment. The fact that she lives in woods is symbolic of freedom -- she is free from the societal expectations. This is especially evident in the scene when Dimsdale spends the afternoon there with Hester and Pearl and they are free to be with one another again. Pearl's name is symbolic. It represents something to be treasured, as Pearl is by Hester, even though having this child out of wedlock is the outward sign of Hester's sin.
Because this novel is considered an allegory, most every detail in the novel could be considered to have symbolic signficance!