How do I install my car seat using the vehicle's lap/shoulder belt for backless booster mode?

To install in backless booster mode with a car’s lap and shoulder belt, place your child in the booster and route the seatbelt through the green labels of the belt path. Ensure both the lap portion lies low across the hips behind armrests, while the shoulder part fits snugly between neck and edge of shoulders without interference from the vehicle's head restraint.