an advertisement / infographic for rack studs - plastic things that on one end have a latch that fits a square rack hole, and on the other end have a threaded rod, which can go through a hole in your rackmount equipment and then you screw a long nut on top of it
https://media.mstdn.io/mstdn-media/media_attachments/files/113/992/622/669/035/637/original/e9f647d99111240f.jpg