What does the clock that Patrick gives to Charlie mean?

In The Perks of Being a Wallflower, protagonist Charlie and his friend Patrick have an odd relationship. Charlie at first thinks that Patrick is dating his crush, Sam, but then finds out that they are only step-siblings. Further, Patrick is gay. All three of them become close friends for most of the novel. Later on in the story, Patrick suffers a bout of serious depression over his relationship with a football player who refuses to come out of the closet, and tries to get Charlie to make out with him. Charlie does let Patrick kiss him, in an attempt to be a good friend. When Sam finds out about this, she tells Charlie that he does not have  to kiss anyone he does not want to kiss. Patrick apologizes to Charlie for being hurt and confused and pushing him to do things he was not comfortable with. He gives him the very messy and terrible clock he has been working on in shop class, earning him a C, as a sign that he knows he is confused and crazy sometimes, but hopes Charlie will continue to accept his friendship.