Safety Rail with just Mattress?

lalabee0425

So we ordered the conversion kit for Keira's bed. It's a Young America crib and the full bed will have those slat rails and just a mattress--no box spring. Can I use one of those safety rails with that? Don't they typically slide between the box spring and mattress? I'm not sure how it would work with just the mattress since the mattress will sit down into the bed itself..... ?  Does anyone use a rail with a bed like this?