The top does not close, but the leaves do not fall out unless you overfill it. These bags are quite large so overfilling them will make them heavy. Wire is inside a casing around the entire top, and that is what makes the bags stand open for raking into. There is a strap near the top for lifting and carrying the bag upright. The strap near the bottom facilitates 'tipping' the bag to dump the contents. I have used mine for 2 years now and am SO PLEASED with them. They make MUCH faster work of corralling and composting leaves from my 23 very mature forest trees on my 1/3 acre property.
The opening is quite large & you cannot fit a 30 gallon plastic bage inside. I tried. I did not want to put out the money for contractor bags as I really feel that they would not work either. You could always put a plastic bag in a garbage can and pour the leaves into the bag that way. The material on these bags is light & there is a wire rim around the front opening. I think I have 3 sets now. I just keep filling them. I really like them.
If you click on buy again then go through all the pictures of the bags there is a very short video showing you how to refold the bags.
Reverse the way they open and secure with a binder clip