I would NEVER-EVER use the two types of chain "links" shown above. Sure they are quick to hook/un-hook but they are WEAK! Check the ratings on them. They will not take a shock load like when a slack trailer chain tightens up.
I only use real clevises and wire them so the pin doesn't unscrew. I use cheap rebar tie-wire. I just cut the wire off when I'm ready to unhook.
