Most toddler rails are made of mesh so that if the child's face gets pressed against it, they can't suffacate. They also typically have a metal bar in a sleeve that sits right at the level of the mattress, or just below the edge, so that hte child can't push the fabric out and becoem trapped between the mattress and the rail. This being said, my 2 year old has a rail on his single bed and still manages to fall out! He somehow manages to roll to the bottom 1/3 where there isn't a rail and roll out of bed! That takes talent! We just make sure that there isn't anything around the bed for him to fall onto. He's been int he bed for almost 6 mo and still thinks he can't get out until we come in to get him! He's laid there for 20 minutes awake without getting out! Goofy thing!