It is a broom handle that rests at the other on the trailer board and yes stops the kink and allows water to drain freely without flattening the battery.
I've seen some captive drains. They are chrome and when you open them, it stays in the boat. I bought one once to fit to my old scorpion but never got round to it. All boats take on water on land it seems so need a natural drain IMHO.
Always slightly concerned if you drill to allow water to drain aft. That could allow water to go forward also.
