Automatic knife?

[Black cat]

When I was a kid I saw an auto knife, you press the button and the blade releases out the front of the handle, when you press the botton again the blade goes back inside.
I've never seen another of these and was wondering what it's called and how does the mechanism in such a knife work?

 

[wall e]

Hoping this works the link for the how it works video on otf (out the front) autos. Illegal in many states. As is most neat or fun things due to some irresponsible or bad people.. Lol
https://youtu.be/0XMpIJ5AspU

 

[Black cat]

Thank you very much! That was a great video explanation and quite an interesting mechanism!