Read the following if you have seen the movie and want to understand it.
(Copied from one of the review-responses)
He obiously felt he was not with the "Train of social society", he had tried to follow it once but realized that it was impossible to do so and also that thats not what he really wants, so he stopped his attempts on becoming a passenger on it.
I thought the hole in the wall as a frightening emtiness within him wich he tries to hide from(by closing his eyes), but is still always afraid of.
The salesman was alittle rough, but my idea was to think of him as how the society is when interacting with the main character. He looks really weird wich is how the main character thinks of society. And his job is to help whoever needs assistance with what his job is, he does what he is supposed to do(fixing holes, repairing problems or whatever), then leaves.
And the part with all that metalstuff in his mouth and in the hole was really rough, thats what Im not sure what I thought about when I made this :p . Mechanics, plumbers, Janitors. They all fix problems, changes things to what its supposed to be like(Its times like this i feel my english is lacking :p), so the salesman had done the thing with the metalpipes and all while the main character was sleeping because thats how its supposed to be, and it looks weird, because thats how the main character thinks about how everything is supposed to be.
And thats kinda it I guess, thats how I thought about it.