The magician tells his audience about a recent visit in an old victorian house that is believed to be haunted. He shows his audience a souvenir from this house: A large brass bolt and nut are shown, the nut is screwed on the bolt and everything is placed on the table.
The bolt is then covered for a second with a silk.
When the silk is removed the audience sees that the ghost in the bolt has unscrewed the nut...Really spooky!