Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 78)

Chapter 5
Installing the Decoder
5–4
You will need four 1/4 - 20 hexagon-head capscrews with flat and split
lockwashers and nuts. Select a capscrew length that equals the thickness of
the mounting surface, plus the thickness of the washers, plus at least 1/4-inch
(12.7 mm) to accommodate the nut and mounting brackets of the decoder.
Figure 5.3 shows the fasteners used for a typical installation.
Figure 5.3
Fasteners Used to Mount Decoder