Yes, I've made racks, both "built in" where it's part of the room structure and "upright" where I plop them on the floor and can move them around.
Racks as part of the room structure (with the countertop became a standing producer's desk)
And a rack that's not attached to anything and can be moved, though with 33U of heavy recorders, hard drives, and amplifiers, ya ain't moving it. I made it wide, deep, but not tall so it fits under my studio desk. I was running out of space to put/make racks so I had to start eating up my legroom
I bought the rack rails from a supplier on ebay fairly inexpensively, and used them in both places, by bolting them through a piece of wood as you can see in both rack types, above and below this text.
In case you're interested, I also made an open-frame studio desk, with adjustable "feet" sticking upwards so I could place non-rackmount equipment like mixing consoles across the width and adjust the height. Being open frame, there's no shortage of room for wiring and nothing blocking their paths. Plus, it was an excuse to rid myself of tons of scrap steel I've been collecting for years.