[adrianmonk]

I once helped a friend move a mattress set up a tight stairway. We got the mattress to turn the corner by brute force squeezing and smashing, but the box-spring was too rigid for that.

We were stumped until we finally figured out that if we simply unscrewed the two wooden frame pieces that run lengthwise, what remained of the box-spring was wooden pieces that run crosswise and are attached to a network of springs. Then it was possible to fold it into a U shape.

To explain visually, the box-spring was built like this one:

https://mk0mattressclarcyl3h.kinstacdn.com/wp-content/upload...

We removed the two pieces of wood running along the left and right bottom edges, then we folded the whole thing so that the wooden cross pieces at the foot of the bed and head of the bed touched each other. The wire grid at the top was just flexible enough to handle a gentle arc.