How does this heater box retainer rod (J-hook) work?

Your pictures seem to clear up my questions. So my next question is does anyone have the correct rod set up that I would need for this box? Will it be workable with this situation that I have or could I even rig up something that would work appropriately? To be fair, a FABO member sent me the retainer rod that I have free, so I can't complain about that. Now I just want to get the right part to make this work. Thanks for all of the information.
----I have one.-----+I replaced mine after losing it, then found it later. Don`t remember what I paid the guy for it tho.+