When your child has outgrown the forward-facing car seat's height and weight limit for using a harness, use a booster seat with a regular lap and shoulder belt. Booster seats raise your child up so that the vehicle's lap and shoulder belts fit properly. Adjust the shoulder belt to fit across the shoulder, not the neck. Use this type of seat until adult seat belts fit your child correctly, usually when your child is about 4.75 ft (1.5 m) tall and age 8 to 12. Secure the car seat in the back seat of your vehicle.