I had a Snapper way back when that had a similar bag. Let's see, if I remember right, the opening of the bag is a big square when open, and there was a plastic stiffener sewn in to the edge of the opening. Push in on the center of the opening on each side, and that brings the outside edges in, and the top and bottom together. It folds up, sort of accordion style. Then that black plastic thing slides over where the folds come together, trapping that plastic stiffener, to hold it shut while mowing. There should be a curved rod/handle/hook that loops itself over the mower handle to hold the back end of the whole thing up while you mow. I think there was a length of rope that went through a hole in the end of that black plastic clip at one end and tied to the rod/handle/hook at the other so you didn't misplace the black plastic thing. Made it get in the way when dumping the clippings more than anything.
Hope that helps. I can picture it in my head, but don't know if I explained it very well. Like you said, pictures would help more.
Hope that helps. I can picture it in my head, but don't know if I explained it very well. Like you said, pictures would help more.