@hywel wrote:

I really like metal bondage because it is impossible to escape without the key

Yes indeed! The key becomes a symbol. Anybody can untie ropes or unbuckle leather straps, but only The One Holding The Key can open the captive’s locks.

Most handcuffs take a standard key, but there are high security handcuffs with unique keys. They’re generally very well made, good looking and often more comfortable than regular cuffs because they’re designed for long-term wear by prisoners being transported. I think they’re ideal for bondage.