This Tailgate Bar is used on the Hard Top version of the BackBone only when the hard top is removed. On the hard top BackBone, there is a gap created along the tailgate so that the rear glass window can close. The tailgate bar covers and seals that gap when the hard top is removed and provides water resistance as well as a surface for the soft top tailgate bar to shut against when using a soft top, thereby securing the soft top rear window.