Although this is not answering your question, I had read (and I apologize that I cannot cite the source as there is all kinds of conflicting information out there) that bed rails are not necessarily safe for your child.
What we did is put the crib mattress on the floor and move it out from underneath the bed until she stopped falling out of bed. We did it for a month, but I really only think she fell out the first week and nothing after that. By the time she got used to the bed and stayed in bed, our little one arrived, and he is still not in the crib any way.
Our daughter was 25 months when we transitioned her.