I want to try to make some flood gates for our doors and they are very
expensive to buy. I want to use some sort of fixing that I can screw
into the wooden door frames permanently. These would have a thread in
the centre that I could use to bolt through, I imagine, external
plywood to create a tight fit as needed.

I have never seen anything like that, apart from rawlbolts which are
not designed for wood so far as I know. Does anyone know of such a
thing, or have a better suggestion? Many thanks.

Regards

Jonathan