When I moved into my current house, I slept on a mattress on the floor for the first few days. The house has all hardwood floors. One of the first nights there, I swear I heard a skittering of claws/nails across the floor that brought me out of a deep sleep. Heart racing, I bolted upright and thought I’d be surrounded by a rat army. But…no. I never did hear it again or find out what it was to begin with.