crosses to bear
On the carpenter-Christ theme, another powerful image from the film is that of the carrying of the wood planks over one shoulder - like so many images of Christ carrying his cross. The man and boy carry them separately, and then near the end they carry a single larger one together - as if, instead of each having his own "cross to bear," they are coming closer to the realization that they are both sharing the same burden.
I don't think I explained this very well, but I think you get the drift.