What part of the seatbelt must be locked at all times for proper car seat installation?

For a proper car seat installation, the lap belt must be locked at all times to ensure that the car seat is securely held in place. When the lap belt is engaged correctly, it restricts any forward movement of the car seat during a collision, providing crucial protection for the child.

While the shoulder belt and retractor mechanism are important components of the seatbelt system, they primarily function to secure an occupant in the vehicle rather than directly securing the car seat. The locking clip, although it can be used in specific situations to lock the shoulder belt, is not a required component for every installation. The primary focus is on ensuring the lap belt remains locked, which is foundational for the overall safety of the car seat as it relates to the vehicle’s seatbelt system.