I always wanted to create an Assassins Creed style hidden blade. And I have now managed to come up with a design idea which should open and close with a flick of the hand.
If anyone is going to make this, please remember that THIS IS NOT A TOY and using sharp object can be dangerous. Therefore I advise you use a plastic or wooden blunted blade or hook instead.
(This is my first instructable so I would be grateful for any comments and improvements)
Step 1: The Idea
This is my idea. Basically, it is created using a drawer slide, a flat spring, a stretchy spring, and a pushing spring. Also, you will need a blade of sorts, some kind of cord/thread, and a ring. The ring releases the flat spring from the notch/end of blade when pulled, either opening or closing the blade, depending on it's current state.
Step 2: Alternatives
An alternative to using the mechanism as a blade would be to use it as a hook, or a quick-release holder... Experiment and see if you can find a way to use it for something else.