3Com CoreBuilder 9000 Getting Started Manual page 27

Installing the OC-3c/STM-1 Daughter Card or OC-3c SMLR Daughter Card 27
Figure 4 OC-3c/SMLR Daughter Card with Protective Plugs
The daughter card's RFI shield may occasionally move in shipping. If the
shield has moved, the screw holes on the front panel might be blocked,
preventing installation of the daughter card. If this is the case, gently slide
the shield towards the center of the front panel of the daughter card and
align the screw holes of the front panel with the shield. Do not remove
the shield. See Figure 14 for a close-up of the RFI shield on the
OC-12c/STM-4 daughter card.