In addition to a single jaw swinging in from one side (which I haven't seen), two jaws swinging to meet at the middle (seems to be described as the "Reese" type), and a straight bar sliding across, there are also rotary jaws that are run by a gear-toothed rack and rotate around the pin to move an opening in the jaw from the back (to hitch/unhitch) to the front (to tow). That rotary jaw looks secure to me, but I would wonder about lubrication and jamming issues; however, I don't have personal experience with any of them.
The rotary jaw is used by PullRite in their fifth-wheel hitches, and is illustrated in the Super 5th Owners Manual
, page 7. PullRite is mentioned in the RV.net discussion, although either they have two jaw designs or at least one poster there doesn't understand (or is unable to describe) how their hitch works.