For the zoomer. This was a common method to rewind a cassette. Why would you do this instead of using the rewind button or playing an unwanted song from the opposite side? Because Walkmans use AA batteries and they are not cheap. This method saves battery when you don't have a Power DC adapter. A BIC pen or a pencil were more common at hand than manual audio cassette tape rewinders, small cranking plastic devices for the same purpose.