We actually didn't use a bed rail. We dismantled DD1's bed and put the mattress on the floor for the first few months until she wasn't moving around as much. When we moved into this house we put her bed back together and she has been on it ever since.
We are getting ready to do this with DD2 in the next few months, as we will need the cot for #3 not long after she turns 2. Until then we will use the bassinet.
Bookmarks