Why did L trust the handcuff so much? Episode 20


  L: If I die, as long as I have this (handcuffs), you'll share the same fate as me


Okay, excuse my language, but what is up with that? It's just a handcuff, you'll be able to chainsaw it or something!

If L thought that far and actually made the chain indestructible (Maybe he used titanium or something!?), we would have probably been able to pick it.

IF (highly unlikely) L actually took every precaution, L's body is not going to be as strong as the metal.

So why did he trust it so much? Was it a bluff/joke?
It was indeed a bluff made by light


   He had Rem write in the death note before the following fake rules that were going to prove that Light and Misa were innocent under any accusations as being Kira, "If the owner of a Death Note does not use the notebook after 13 days time, he or she will die" and "If the Death Note is burned, torn up, or otherwise rendered useless, any people who have touched the Death Note will die". With Light and Misa having no contact with the death note for more than 13 days, since they were both confined, and neither of them had died, that would prove to L that neither of them were Kira. L agreed and he finally took the handcuffs off of Light.


Following this info it would mean as long as Light is bound to L he could not use the notebook. Meaning he would die after 13 days, this would render the book useless so L would die as well as he touched the book before hand.