Where are the instances of power in Endgame, and how they relate to the themes of the story?

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...