heater box flap door install

anyone know how to install heater flap door with the hook going up in to the top portion of heater box to connect to cable? i did not remove this part so i have no idea on how it goes back in, see pics below.thanks

Here is a photo of that door. I believe the arm just slides up into the hole then drops down into the lower hole. Can't be a big deal or I would have taken more photos.

thanks again.

what model is this?

69 b body. i got it install it took some wiggling and patience to get that hook in the hole and turned the right way.