You know you have one. Or two. Or thirty. They’re boxes, maybe left from the last time you moved, maybe when you did some previous organization and stashed stuff away. And today we’re dealing with them. No matter how many you have, pick one, open it up, and deal with what’s in there. Put it away, throw it away, whatever you have to , but don’t stop until it’s empty and you can break the box down and stash it with the recycling.