rbrtrbnsn — 9 years ago(December 28, 2016 08:34 PM)
It's a metaphor for locking away painful memories. Like an aching tooth that inexorably draws your tongue to it, he couldn't help but revisit old memories by unlocking and going down to the basement.
I viewed it that he valued the memory of his wife so much that he protected it with a lock only accessible to him. He didn't care about anything else as he didn't lock his house and was more than happy to destroy his door.