Everyone who wrote comments about the need for the string to be tight inadvertently revealed themselves to be quite advanced in age. I doubt any kids have done this in the past 40-50 years. And yes, I made one of those devices a LONG time ago.
Comedian George Gobel appeared on a segment of The Tonight Show in 1969. He entered after Bob Hope and Dean Martin and made the comment to Johnny Carson about coming on last and having to follow those two major stars to which Carson, Hope, Martin and the audience came unglued with laughter. After the laughter subsided, Carson asked Gobel about his career in World War II as a fighter pilot to which Gobel replied that he had spent the entire war in Oklahoma, pointing out with mock pride that no Japanese plane ever got past Tulsa which invoked another huge round of laughter. Gobel also began getting unsolicited laughter, being unaware that Dean Martin was surreptitiously flicking his cigarette ashes into Gobel’s drink. Observing all of this, Carson finally asked rhetorically, “Exactly what time did I lose control of the show?!”
For younger readers who may not get this, it is a spoof of the 1973 movie ‘The Exorcist’ in which the young girl, Regan, is possessed by a demon.