Dell PowerEdge T605 - Manual (Page 109)

Installing System Components
109
7 If you are removing the card permanently, install a filler bracket in the
empty card slot.
NOTE:
Filler brackets must be installed over empty expansion card slots to
maintain Federal Communications Commission (FCC) certification of the
system. The brackets also keep dust and dirt out of the system and aid in
proper cooling and airflow inside the system.