Most people (us included) find Beckett to be a challenging writer. There is a big temptation to read his work as a metaphor and to ignore the physical realities that are a part of it. It's easier to just take away the gist of a Beckett play rather than focusing in on all those gritty particular details (of which there are a surprising number considering that Beckett is a minimalist).
To take but one example from the play: Hamm keeps his parents in trash bins. Symbol! Hamm treats his parents like trash. But notice, also, how Hamm's parents were in a bicycle accident where they both lost their legs. Now they have nothing but stumps. The trash bins are filled with sand for these stumps, and Hamm assigns Clov to change it from time to time. This is not just a symbol; it's meant to be real. The play is vivid and it is continuous, and it is chock-full of little details.
This is not to say that there are no symbols in Beckett's work, but notice that every symbol ultimately comes back and ties us into the reality of the situation. Anyway, enough of that; let's talk about a few symbols.