A tower device for supporting a crossbar over the roof of a vehicle includes a tower body, a clip retention mechanism and a clip selected to adapt to a particular vehicle profile. Various mechanisms may be used to secure the clip to the clip receiving mechanism. For example, a lock body may insert through coinciding apertures in a clip and clip receiver. A spring retainer may slide into slots or grooves in the lock body to prevent the lock body from disengaging. Other mechanism employ lock mounts that pivot to swing lock bodies through apertures in the clip and clip receiver.