Apple Macintosh Performa 6400 Series - Manual (Page 144)

If the card does not have a hook on it, simply pass the external connector
through the opening in the vertical plate as shown here. (Some cards have an
external connector that protrudes out of the opening; others, like here, have a
flatter external connector.)
5 Passing the external connector through the opening in the vertical plate, insert the
card into the communication slot. Press down on the card until the connector is solidly
in place.
Don’t force the card. If you meet resistance, pull the card out and try again.
If your card has a hook on it, make sure the hook catches between the layers
of the vertical plate.
6 To see if the card is properly connected, lift it gently. If it resists and stays in place,
it’s connected.
7 If the communication card you installed is an Ethernet card, see if you need to install
software with it. Install it if you need to.
Communication slot Vertical plate
Opening in vertical plate
Communication card External connector
144 Chapter 9