Bananas had the job of requesting a new spray gun for the monkey houses hosepipe (my blog), and eventually the zoo supplied such an item. Our old one got broken/jamed.
The new one came with two connectors and while it was easy to guess what one did the other kind of stumped the whole monkey house.
With no instructions we eventually figured out that the other end connects to a tap, which of course in our case is fine.
We apes all laughed while the logic of providing two connectors sort of makes sense it also does need a pipe that is not supplied. Should you be replacing a part then the other adaptor is a bit confusing.