NEC Express 5800/320Lc User Manual page 346

8-36 System Upgrade
8.
Align the PCI board with the guide rail groove and insert the board slowly.
IMPORTANT:
installation. Note that if excessive force is applied to the board, it may be damaged.
9.
Attach the retainer bracket to fasten the PCI board.
If the insertion is unsuccessful, remove the board once and retry