World Trade Center: Secrets of a skyscraper window cleaner
After two window cleaners endured a terrifying ordeal 68 storeys above the ground at the World Trade Center, many watching around the world wondered who would do such a dangerous job.
Juan Lizama and Juan Lopez held onto the nearly vertical platform for almost two hours after a cable holding the platform malfunctioned.
The pair were eventually rescued after firefighters cut a hole in the glass.
The BBC spoke to Andy Horton, a veteran window cleaner and safety trainer in New York, about the dangers of working hundreds of feet above the city streets.
Produced by the BBC's Anna Bressanin.