We have had some of our awesome Jeep enthusiasts write in and ask about some C plate installation issues that they have had on their Jeep JL mud flap install.
There are a lot of parts with this hardware kit, but the screws provided will work and you do need the plate to keep the nut from backing out.
First, confirm that you are using a 5/8" screw, then with C plate removed, tighten the screw onto the nut so that the head is against the material. Tighten 1.5-2 more turns to really seat that nut on. Undo and replace the C plate and you should be able to catch the nut to tighten.
We designed it to be a close fit so that the screw did not stick out the back of the flap. This keeps everything clean and eliminates potential catching.
You are welcome. ;)