I have a variable speed YS Tech fan, and after reading this thread, I took a pci slot cover from my Lian-Li and drilled a 1/4 inch hole in it. I needed to enlarge that hole just a bit. Then I drilled a little hole off to the side for the little metal prong. Everything matched up, and now I have my YS Tech fan control knob sticking out the back of my computer. The best part is that if I want to remove the YS Tech fan for any reason, I just pull off the pci cover. Worked slick. Thanks mechBgon. Good idea.
Previously I just cut a piece from a mounting square and stuck the adjuster on top of my hard drive mount.