I think they were a set of these little metal spring thingies that clamped onto and stuck out from the lower edge of your car and made a noise when they hit low lying objects like curbs, tree stumps and the kid's trike. My grandmother had them, along with a suicide knob, on her old Studabaker. (A suicide knob is a doorknob type thing that screwed onto one side of your steering wheel and made it possible to turn sharply by grabbing the knob and using it to rotate the steering wheel. They are now illegal.)
Blessings,
Barbara