Brake line fittings

[Fenix]

Is anyone familiar with the fittings in the attached picture. I need to change the length of the brake line so need to disconnect and reconnect these fittings but I don't know how they work. They are not such that they will take a wrench and pushing in on the "collar" does not seem to do anything. I did not try to get really aggressive with them, I'd rather know I am doing the right thing before I add force. Any help is appreciated.

Thanks

 

[Daleandee]

 

[Fenix]

 

[Marc Zeitlin]

 

[TiPi]

 

[Fenix]