May God forbid you ever find yourself with the tables turned and bad guy has you locked up. Even though the chances of that happening are slim at best, there is certainly nothing wrong with preparation. There are many excellent law enforcement-military resources that teach escape and evasion. Another good resources to learn from is bad guys themselves, as their methods are crudely simple and of course, well proven. Here in this video, an inmate demonstrates escape from handcuffs that have been applied in text-book fashion, and doubly secured with a black box.