Dell Precision T3400 (Late 2007) - Manual (Page 173)

Adding and Replacing Parts
173
10 Reinstall the card retention cover, if removed.
11 Close the card retention cover by snapping it into place to secure the
card(s).
12 Close the card retention door by snapping it into place to secure the
card(s).
1 release tab 2 card retention cover
3 card retention door
3 1 2