Mary Beatrice Davidson Kenner (1912–2006) always had trouble sleeping when she was growing up in Charlotte, North Carolina. Her mother would leave for work in the morning through the squeaky door at the back of their house and the noise would wake Kenner up. “So I said one day, ‘Mom, don’t you think someone could invent a self-oiling door hinge?’” She was only six at the time, but she set about the task with all the seriousness of a born inventor. “I [hurt] my hands trying to make something that, in my mind, would be good for the door,” she said. “After that I dropped it, but never forgot it.”
You could say that skill and ingenuity was in Kenner’s blood. Her maternal grandfather had invented a tricolor light signal to guide trains, and her sister, Mildred Davidson Austin Smith, grew up to patent her own family board game and sell it commercially. Her preacher father, Sidney Nathaniel Davidson, even made a go of transforming the family hobby into a full-time career. Around 1914, Sidney patented a clothes presser that would fit in a suitcase and press trousers while a traveller was en route to his destination, but he turned down a New York company’s $20,000 offer in favour of attempting to manufacture and sell it himself. The result was a failure: he produced only a single presser, which he sold for the paltry sum of $14.