This is a mod I created for the Jonsbo N4 case. There are already some great mods to help with cooling, but none of them help with airflow out of the top of the case. This mod allows for two 120mm fans to be installed on top of the motherboard with the airflow blowing out of the case.
The three pieces are attached together with m3 countersunk screws. I used these rubber feet for the bottom of the two legs where they touch the case, and I used two fan screws to attach the other side wall through the holes.
I used some Thermalright TL-C12C fans. These are very quiet and very reasonably priced. Really though, any 120mm fans should work.
The tray holds two 120mm fans side-by-side, but it's a pretty tight squeeze! You'll probably have trouble if you try to stick one fan in at a time. The trick is to put them both in together. Angle the edges that touch upwards a bit, so they make a little point, kind of like a roof. Make sure the tops of the fans are lined up perfectly, and then push them both down into the tray at the same time. This way, one fan's edge won't get stuck under the other, and they'll slide in nice and easy.
The only permanent change you'll have to make is to flatten a little over half of that lip inside the top piece. I used pliers to start the bend, then a hammer to finish flattening it. Just be sure to have the top side on something soft like a wooden workbench, otherwise you can do some cosmetic damage to the top side. I'm honestly not even certain what the purpose of that lip is since it doesn't help with locking the lid into place.
The author marked this model as their own original creation.