780T Additional Fan Mounting

I dont know how to mount the additional fans, such as top and bottom. The locations where there are fans, have holes that can accept screws- ie they have screw sized holes, and teeth to take in a screw. The top/bottom fan mounting holes are gigantic, way too big for fan screws, nor do they have teeth for a screw to grab onto, and screw in. How does Corsair expect us to mount fans in these locations?? I have purchased Thermaltake Riing 140mm RGB fans. The fan screws are typical, but WAY too small to fit into these mounting holes. . . . even if they were gigantic screws, the holes have no teeth to accept a screw. I just dont get it. Am I supposed to buy some kind of mounting set up, or is this just a huge lack in planning on Corsairs part? Does no-one actually use these fan mounts? There are absolutely no instructions in the manual at how to use these other locations.... I dont know how to contact Corsair tech support, I hope someone can help me.

As far as I'm aware, the case holes don't need to be threaded, the screw thread just goes through the case, from the outside, and screws into the thread on the fans. That's how mine have always worked.