Bed Safety Rails

Will will be moving Ben out of his cot when the new bubba arrives, he will be 20 mths.

The problem is he is very active in his sleep, he normally wakes up at least once in the night as he has moved up the cot or twisted himself around and hit his head and he is always at the opposite end of the bed upside down and sideways in the morning or standing up!!

So I am scared he is definately going to fall out of bed, with the safety rails, do they just climb over them in the night, thus falling further? or do they stop them?, is a mattress next to the bed on the floor a better idea?

Any suggetions/ideas that worked for you would be great

Thanks Ladies

ditto to what emma said.
i tried gabriel out for day sleeps first in the big bed to get him used to it too.