I don’t think they NEED to be different, but that they are using a common clip. The ones up the sides and across the top have to be different because the ones that go on the bottom are too long and won’t fit up the sides and along the top due to the depth (or lack of) next to the fence. If you used the short fat black clips all the way around, it would probable work just fine. Since they come as a kit, I didn’t mess with it.
