You would not believe how much consternation this simple question has caused my office. :)

When installing cage nuts to mount rails or equipment, the nuts are clipped into a piece of metal with square holes, usually labeled with the rack unit number:

A rack with the part being asked about highlighted

... as highlighted in red.

How does one refer to this part of a rack?

  • 3
    I'd call that the "post".
    – joeqwerty
    Mar 27, 2018 at 20:55
  • 1
    The only place I'd be putting a cage nut, is the cage. :) Mar 27, 2018 at 21:41

2 Answers 2


Mounting Flange. It's defined in "EIA-310-D, Cabinets, Racks, Panels, and Associated Equipment". It may not be easy to find a legitimately free (the EIA charges for it) copy online, but you can find plenty of references to it.


I've never heard a specific name for only that exact part of the rack.

Like @joeqwerty said, usually it's just called the post. A standard server rack is called a "4-post rack", and there are "2-post racks" which were (are?) common in telco use when the gear to be mounted is a bit lighter in weight.

However, that really refers to the whole piece of metal, not just the part which the cage nuts attach to. So @luke-peterson's suggestion of "cage" is probably the closest thing to just the part you're trying to name.

  • Calling it the "post" seems fine to me. Mar 27, 2018 at 23:07

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