Dark Room
Douglas' dark room where he develops the pictures is a metaphor for his life. He lives completely in the dark where he does as he pleases to satiate his sexual appetite, while appearing to the world as a "good dad."
Mt. McGinty
Mt. McGinty is on fire during the beginning of Act III. This is a metaphor that just like the Mt., the family home is in flames, it is barren and dry, just like the land and it is about to erupt in fire.
Loved
Jack hugs on Alan at the end of the play and doesn't want him to go. This is a metaphor for how Alan desires someone, his father, to tell him he loves him and wants him to stay--something that he will not get from Douglas.
Photography
Ronnie allows Douglas to take photographs of half-naked women as a hobby. It is a metaphor for how she allows him to do the wrong thing, though she knows it is wrong and closes her eyes to it in order not to start a fight.
Headache
As soon as Alan arrives in San Diego, he gets a tormenting headache that lasts three days because of the change in altitude. This is a metaphor for how Alan is drastically effected by the change in environment, one that is instantly toxic to him, which is in the presence of his father's home.