Key symbolism

Even his neighborhood was in the shape of a key.
Not quite sure what the symbolism was meant to convey though.
Anyone else smarter than I that can offer an answer?

I guess religion has a lot to answer for!

Quite a study into mental decay as well as physical even to his plants.
The movie itself just felt like decay right up to the end.
Great photography not much you can really say about the movie - quite sad really.