39 ford coupe wiper arm attachment

[zipperhead]

Hoping someone can shed some light on how the 39 ford wiper arm is supposed to be assembled. Is there anything on inside of roof (where threaded end goes through that secures It or does it just float there? I understand that there is supposed to be a hex nut on outside to secure chrome bezel and pad then wiper goes on and then end nut but still seems a little sloppy. Maybe the pressure of the wiper arm/ blade is supposed to hold it secure enough?

Thanks