When your child upgrades to their first bed, use a rolled and tied beach towel (or similar) under the mattress protector and fitted sheet to stop kids from falling out of bed. This great idea was given to me by a patient when our daughter upgraded from a cot to a bed. It is much cheaper and easier to fit than a wooden bed barrier and less likely to cause harm if a child were to land on it when playing. The rolled towel also enables the child to easily hop in and out of bed on their own if they need to.