One theme of the play is how the characters must depend on each other for their survival. Since Hamm is the only one who has the combination to the cupboard, he exercises control over Clov, who depends on Hamm to provide him with food. Clov has power over Hamm because he is Hamm's eyes and legs. Hamm's parents, Nagg and Nell, are dependent upon Hamm as well. They have no legs and live in a trash can filled with sand. They depend on Hamm and Clov for their survival since they're unable to move as well.
Life and death is another theme in the play. The characters live in one room in a world that can't sustain life outside. All of the characters are crippled, even Clov, who can't sit down because of his legs. Each character wakes each day wanting it to be the last day, since none of them has anything left to live for. Nell, Nagg, and Hamm are unable to end their lives without Clov's help, so Clov has that power over them. Clov continuously threatens to leave, an act that would end his life.
The conflict between Hamm and his parents is shown in the theme of the generational conflict, especially between Hamm and his father, Nagg. Hamm especially resents his father, and he has total control over the lives of his parents. They are dependent on Hamm, since he has the key to the cupboard, and also on Clov, who must bring food to the couple.