Bunk House Safety

I like the noodle idea if it works for you. I made a small rail and used angle brackets, like the big thick ones that could mount on a wall and hold a shelf. I screwed one leg of them through the floor of the upper bunk so the other leg would come up out from under the mattress, and then I attached a couple of upright wooden pieces (mostly for better looks than the galvanized steel) and a cross piece. It didn't go the full length but left the foot and open near the ladder just enough that if they did fall out it would be a feet first type of thing that should wake them before it happened. It only attached with screws under the mattress.