The First Years Secure Comfort Fold-Down Bedrail is designed to help your child - and you - feel more secure at bedtime. Unlike older bedrail models, this bedrail is designed to fit securely on your child's mattress - without slipping away. Plus, to protect children who move around their big kid bed, we created a rigid design to help reduce the risk of getting caught between the bedrail and mattress. Fits most twin, full, and queen mattresses.