Numbering the Vertical Rails
When you install a system in a cabinet, you first need to number the vertical rails, if they are not already numbered. To do so, use a marker or pencil to number the holes of the 2U in which to install each system.
The cabinet rails, system, and various components are measured in Electronic Industries Alliance (EIA) rack units (U). Every three holes on the EIA square-hole pattern on the vertical rail equals one U (1.75 in., 4.45 cm). The holes on EIA rails are in a repeating pattern of 1/2 in. (1.27 cm), 5/8 in. (1.59 cm), 5/8 in. (1.59 cm), as shown in Figure 11. The middle hole of each U has equal spacing between it and the holes adjacent to it. In some cabinets, numbers on the vertical rails identify the middle hole of each U.
Figure 11: EIA Vertical Rail Hole Pattern
To number the vertical rails
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On each of the front and rear vertical rails, number the 2U spaces where you will install the system.
Notice: To ensure that the components will be level when you install them, mark the same holes on the rear vertical rails that you marked on the front vertical rails. -
If you are installing additional systems in the same cabinet, continue numbering another 2U for each system.
To continue with installing a system in a cabinet, see Preparing the Support Rails for Installation.
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