For example, I often bring up images of card catalogs when explaining database indexing. As soon as people see the index card, and then see that there is a wooden case for looking up by Author, a separate case for looking up by Dewey Decimal et. cet. the light goes on.
However, the metaphor isn’t that educationally helpful anymore. On more than one occasion I found myself explaining how card catalogues or even (book) dictionaries work, only to be met with the reply: “oh, so they’re basically analogue hashmaps”.
But nope, its because a punch card was 80 characters wide. And the first punch cards were basically just index cards. Another hat tip to the librarians.
I guess this is the computing equivalent of a car being the width of two horse's asses...
Both band directors showed up at one of my classes the first day of school, dragged me to an empty room, and browbeat me into returning to band. It was the right choice for my social life, but I did hear great things about that class.
Context and preconceptions are everything!
I just explain that hard disks are just a continuous list of 1s and 0s, and then ask what we need to do if people want to find anything. People are able to infer the idea of needing some sort of structure.