Computer rack / cabinet (commonly called a rack) is a metal frame used to hold various hardware devices such as servers, hard disk drives, modems and other electronic equipment. Some may refer to a rack as "LAN or network furniture" as resembles a shelving structure where components can be attached vertically, stacked on top of one another. A computer rack can also be called a relay rack or open rack.
Generally the individual devices are screwed into the front, which has tapped metal strips with spaced holes to accommodate the height of the devices, usually 1.75 inches of space is between each hole (measured in U).
While racks come in many different shapes and sizes, the standard (traditional) size rack is 19-inches wide. Racks are usually made of aluminum or stainless steel. The Electronics Industries Association (EIA) establishes standards for cabinets and racks intended for use with computers and other electronic equipment.
The terms rack and cabinet are often used interchangeably, which is incorrect. The rack refers specifically to the frame that provides a means for mounting electronic equipment, while a cabinet is fitted with doors and side panels.