AT&T 75 Wiring Manual page 264

110-TYPE HARDWARE
11. If a vertical patch cord trough is to be installed, partially install the first screw for
the patch cord trough, on the line, 7/8 inch (2.2 cm) from the previous screw.
Partially install the second mounting screw 5-5/16 inches (13.5 cm) from the screw
just installed. Repeat steps 3, 4, and 5 above.
12.
Repeat steps 10 and 11 until all the terminal blocks and vertical patch cord troughs
in the Distribution Field have been installed.
Figure 3-29. Mounting 300-Pair 110P-Type Terminal Blocks (Approximately
288 4-Pair or 384 3-Pair Station Capacity Illustrated)
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