When bagging with the lawn mower, I hate how the flap slams shut when you remove a full bag. Then, you have to reach down low to pull that flap up to reattach the now empty bag.
I've solved the problem simply. It keeps you from having to bend so low!
Loop a small shock cord (or bungee cord, if you prefer) around the lower cross bar of the handle. Hook the free end into the flap. It should be loose enough to allow the flap to lay against the bag. When you lift the handle into the bag removal position, the flap gets raised with it. When you fold the handle flat for storage, you must unhook the shock cord first! Look at the pictures. It really is simple and really does save your back!