I'm not even sure if 'blind' is the right word. What I'm after is a tank connector that one can use on a tank where one can't get to the inside. I have a number of barrels (HDPE) that I want to use to collect water but they don't have removable tops so I need a way to fix an outlet without being able to get to the inside of the barrel.
(It would also be useful in one tank where I *can* get to the inside but it's so deep that reaching down to hold the connector is an interesting exercise)