hang by a nail

To hang or dangle from something with a nail serving as the only means of connection, intentionally or unintentionally. You better go get your toolbox because that board is hanging by a nail. The psychiatrist's office offered little in the way of decorations, save for a large, framed degree hanging by a nail above the desk. I'm amazed that wreath hasn't fallen off the door yet—I mean, it's only hanging by a nail!