The Joker is NOT on the cover of Detective Comics #40

I would assume Robin was falling from above and then latched on.  Daredevil's always hanging on flagpoles.  Spidey as well for the first couple decades.   

Any of y'all do a flagpole or awning count in your downtown areas?  We hardly have any.  Probably why all the superheroes are in New York.  Maybe it's a Union thing that requires those.