Bunk bed guard rails for kids

We used hot glue to attach three pool noodles in a triangle shape. Then we attached the noodles to the mattress cover with some fairly thick thread. Makes a lip about 4-5" tall so the kiddo (8 years old) won't roll off. It looks like this setup from amazon: www.amazon.com/2-Pack-hiccapop-Bumpers-Toddler-Water-resistant/dp/B01DTBFB5U.

Don't know how it's framed but ours sounds a lot like the walls when tapped on so I'd guess foam bonded to that 1/4" almost wood stuff. If I planned to bolt a real bed rail to it I'd likely go all the way through and use big fender washers on each side to distribute the load.

Good luck!