Zedebee said:
It will tidy up the engine bay if you use the correct rivets or fleabay equivalents. They can be a pain in the ar*e if the plastic cover is not exactly aligned, as the rivets (which screw in) can twist and bend, and break. Have a couple of extras handy.
You don't have to screw them in. They are designed to screw out. But to fit them, place them squarely in the hole then use something like the end of a screwdriver handle and sharply tap them straight down.
I used these:
https://www.ebay.co.uk/itm/371743089000