Bed safety rails to stop toddlers falling off

Our grandson is nearly 2 and is still currently sleeping in a cot.  However, we want to take him on holiday with us for a few days, so he will have to sleep on one of the single settees in the lounge area, but I am worried about him falling off on to the floor.   Has anyone ever used any of the children's bed safety rails that you can get in these circumstances?  Was it easy to use and was it successful?  Thanks very much.