Apple Video System - Manual (Page 15)

7 Locate the video-in access cover on one side of the vertical
plate attached to the logic board. Remove the cover from
this opening by squeezing together the plastic tabs that hold
it in place.
Note: Your logic board may not look exactly like the one
pictured here, but the video-in slot and plastic access
cover are in the same position regardless of the logic board
you have.
Video-in slot
Vertical plate
Plastic tabs
The plastic access cover is on the
other side of the vertical plate.
Metal retainer
9 Installing the Card and Software and Connecting Video Equipment