Compaq makes racks for their servers - but you can put other stuff in them. For this, they make shelves. Recently, we inherited a gaggle of racks (5) and one shelf. The shelf did not have a part number, but we wanted more. So, I called Compaq. I talked w/Tech support, Customer Service, the routing center, the sales team, and a variety of other people. I estimate that I spoke with 10 different people - 4 of which claimed to be actually able to help me. After a variety of dead-end calls, part numbers that did not exist, part numbers that are not in the sales' teams systems (yes, multiple sales teams..), and 4 hours all told on the phone, I called Dell.
Dell makes server racks and shelves for their racks. They're compatible with the racks I have. Their shelves fit fine - how do I know? They sent me one to test out. It fits just fine. Total time on phone with Dell representative (reached on first phone call, I might add) - 20 minutes TOPS. Guess who's getting my vote for ordering these shelves?