Dell PowerVault MD1120 Installation Manual page 13

Figure 1-3. One Rack Unit
1 U (44 mm or 1.75 inches)
CAUTION:
If you are installing more than one system, install the mounting rails
so that the first system is installed in the lowest available position in the rack.
To mark the rack, perform the following steps:
1 Using a felt-tip pen or masking tape, place a mark on the rack's front
vertical rails where you want the bottom of the system you are installing
in the rack to be located.
The bottom of each 1-U space is at the middle of the narrowest metal
area between holes (marked with a horizontal line on some rack cabinets -
see Figure 1-3).
2 Place a second mark 88.9 mm (3.5 inches) above the first mark you made
(or count up six holes in a rack that meets EIA-310 standards).
This mark should indicate the system's upper edge on the vertical rails
(see - Figure 1-4).
12.7 mm (0.5 inch)
15.9 mm (0.625 inch)
15.9 mm (0.625 inch)
12.7 mm (0.5 inch)
Rack Installation Guide
11