Just picked up an APC 48u server rack. There were no pictures of it in the post and I did not notice until I got it home and set up, that the rack rails have threaded holes instead of square cage nut holes. I can’t seem to determine the thread size and pitch, and have a thread gauge coming. Until then, does anyone know anything about this? The people I grabbed it from had used self tapping machine screws and drove them in with an impact wrench. Is this what APC had intended, or is there some $300 proprietary screw I have to buy from them?