IEC 60297-3-101 Deutsches Institut für Normung DIN 41494 - Multiple documents in German but some documents are available in English. DIN 41494 Equipment practices for electronic equipment; mechanical structures of the 482,6 mm (19 inch) series DIN 41494-7 Dimensions of cabinets and suites of racks. DIN 41494-8 Components on front panels; mounting conditions, dimensions DIN IEC 60297-3-100 (see above in IEC section) A rack's mounting fixture consists of two parallel metal strips (also referred to as "posts" or "panel mounts") standing vertically. The posts are each wide, and are separated by a gap of , giving an overall rack width of . The posts have holes in them at regular intervals, with both posts matching, so that each hole is part of a horizontal pair with a center-to-center distance of . The holes in the posts are arranged vertically in repeating sets of three, with center-to-center separations of , , . The hole pattern thus repeats every . Holes so arranged can either be tapped (usually 10-32 UNF thread, or, less often, 6mm metric) or have square holes for cage nuts. Rack unit Racks are vertically divided into regions, in height. Each region has three complete hole pairs on each side. The holes are centered at , , and from the top or bottom of the region. Such a region is commonly known as a U, for unit, RU for rack unit or, in German, HE, for Höheneinheit. Heights within racks are measured by this unit. Rack-mountable equipment is usually designed to occupy some integer number of U. For example, an oscilloscope might be 4U high. Rack-mountable computers and servers are mostly between 1U and 4U high. A blade server enclosure might require 10U. Occasionally, one may see fractional U devices such as a 1.5U server or devices that are just 22.5 or 15 cm in width, allowing for 2 or 3 such devices to be installed side by side, but these are much less common. The height of a rack can vary from a few inches, such as in a broadcast console, to a floor mounted rack whose interior is 45 rack units () high. 42U is a common configuration. Many wall-mounted enclosures for industrial equipment use 19-inch racks. Related standards 10-inch rack Some telecommunications and networking equipment is available in a narrower 10" format with the same unit-height as a standard 19"-rack. 11-foot frame Frames for holding rotary-dial