My EDC carabiner. Truly ED, as I have keys to my flat attached to it.
This type of carabiner is used to attach sail to the mast on the sailboat. I may be wrong because I am not a sailor, but I think it is called "hank". They are tough, completely rustproof and difficult to damage due to very simple gate construction. 6-shape prevent key ring from falling when open. Very simple concept but it works.
It could be attached to the trousers, near belt for example:
but I don't like the noise, so I prefer deep carry in my pocket with carabiner fastened on the edge of pocket:
Oh, and not to finish carabiner thread with only small piece of information let me introduce my anodized beauties from Ocun (Czech Republic?)
and from the Black Diamond (US)
Those are too big to EDC, I use them for climbing and caving only, but they are so nice piece of craft so I just decided to share.
And the action picture of me using those carabiners