In a fit of paranoia, I felt the need for one more camera in case the local populace beat down the doors for my Worldwide Pinhole Photography Day Workshop in Appleton (Turns out I have plenty).
We have a standing order with Oaks Candy for a selection of their historic chocolates. They're packed in sturdy white boxes. All my pinhole supplies are stored in them. My experience with white cardboard is that it's very hard to make truly light-tight. One day as we broke down one of the boxes for recycling, I noticed that it's grey cardboard with a white covering and actually pretty opaque.
The cardboard is thicker than most product packaging. It makes a sturdy box but it required a little on-the-fly adjustment to make it fit right.
As it happened, we needed a resupply the next day. Very satisfying to make the camera's first exposure of the front of their South Side headquarters.