This is not part of a quiz or crossword but as my kittens were playing with an item of packaging yesterday it occured to me that I did not know the correct name for what it was. It was a square ended box but was very long in length and was open at both ends so technically it was a square cylinder. But by definition surely a cylinder is circular so what do you call a square one? Square tube doesn't seem correct either. Is there a proper word for a square tube?
I think you'll have to invent a new word, PtheC. There are 1,620,000 hits for Square Cylinder on Google, but I don't see any other term used.
How about a Kitunnel?