Dell PowerEdge C1100 Guide De Mise En Route page 8

1 Align the end pieces of the rails on the vertical rack flanges to seat the
pegs in the bottom hole of the first U and the top hole of the second U,
and engage the back end of the rail until the latch locks in place.
NOTE:
2 Repeat these steps to position and seat the front end piece on
the vertical flange.
3 To remove the rails, pull on the latch release button on the end piece
midpoint and unseat each rail.
6
Getting Started With Your System
The rails can be used in both square- and round-hole racks.