There's something about them that I love. They have dual possibilities. They keep things private, secluded, secret. They can also open the way, invite, provide a sneak preview, a selective glimpse. They proclaim. They say, come in, there's something in here. They're mysterious, tantalising. They can be welcoming, menacing, perfunctory, unnoticeable. They carry people's names in offices. They indicate wealth, poverty. They have social standing. They accessorise with handles - small, large, impressive, quirky, ugly, inventive. They guard entrances into spaces. They are metaphors.