"Flexible rubber thing with a garden hose-sized connection on one end."
A: "It’s for clearing clogged drains. It works just like you think it does. Put it in a pipe between 1.5” and 3” and it will first expand and then start spraying water to clear the clog."
If I remember correctly that's a book holder, two straps are used to hold the books and that's the handle.
Used on a siphon hose to keep air from entering the vine wile not used, thus preventing vineger growth.
My Dad had some, he'd get them out when we went ice fishing!
Don't Google it, Duckle it!