A rackmount case is a computer chassis that is designed to fit into any standard 19” rackmount cabinet. Special 21” width cabinets do exist, but these are specialist and generally only found in telco’s. All server rack mount cases are designed for a standard 19” cabinet.

All rack mounted equipment (be that a server or other IT equipment) are all measured in Rack U (commonly simply referenced to as “U”). 1U of rack space is exactly 44.4mm in height. 2U is 88.8mm (and so on). Most equipment is 1U, 2U, 3U and 4U in height. A rack mount cabinet can come in multiple forms – It could be an open-frame, a single vertical frame or be various different depths.

The most common cabinet type for a rack mount case is the enclosed type. It will have 4 vertical mounting posts, which have square holes designed for cage nuts. These cage nuts are universal in size and are made by many manufacturers. Cage nuts little snap in nuts that allow for a screw to be installed through the rack bracket (also known as ear) on a rack mount case or piece of rack mounted equipment (such as a router or switch).

For server rack mount cases, typically an extension rail is used which fixes to both the front and rear vertical mounting posts and allow for the server to be easily drawn out of the cabinet on “rails” for easy installation, removal and also servicing whilst still in the cabinet.

A rack mount server case can be used to house computer components, such as power supply, motherboard, CPU, drives etc. A rack mount case is not too dissimilar to that of a PC Case, just in a different orientation (horizontal rather than vertical, such as with tower PC Cases). The only consideration with a rack mount server case is that often more care needs to be taken as to choosing the components that go within – such as the correct type of PSU, motherboard and the cooling for the CPU. Airflow direction is also a key consideration, too.

Below is an excellent graphical example of the dimensions of a rack cabinet.