Which of the following is not a structural support that the roof ties into?

The headliner is not a structural support that the roof ties into, as it serves primarily as an interior finishing component of the vehicle. Its main function is to provide aesthetic value and conceal the internal structures of the roof and any wiring or insulation present. The headliner does not provide structural integrity to the vehicle's roof or contribute to the support of the roof structure itself.

In contrast, roof rails, the windshield, and roof bows all play crucial roles in the structural support of the vehicle's roof. Roof rails provide longitudinal support and can help in distributing forces across the structure, while windshield frames offer lateral reinforcement and are integral to the overall structural design. Roof bows help maintain the shape of the roof by providing cross support, enhancing both the rigidity and safety of the vehicle. Each of these components contributes to the overall strength and safety of the vehicle in the event of a collision or rollover.