Cropped In Her Cage
You might enjoy this nifty scenario I found over at Sex And Submission, featuring a riding crop, an iron cage, and the lovely Sandra Romain:
Spanking Blog: Adult Erotic Spanking At Its Best
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Bondage Ass Beatings Movie:
Detention House 3: Severely Punished Delinquent Girls
"...and then the spanking starts. Brutal, totally uncompromising. You have never heard screams and shrieks as terrible as these..."
Hmm… could be difficult to land with those bars in the way. I’d say a vertical downward stroke is the best bet!