Apple Power Macintosh 7600/120 Series - Manual (Page 158)

9 Press the card gently but firmly until the connector is fully inserted.
m Don’t force the card. If you meet a lot of resistance, pull the card out and
try again.
m To see if the card is properly connected, pull it gently. If it resists and stays
in place, it’s connected. (Make sure you don’t pull the card so much that
you accidentally disconnect it.)
If you have other cards to install, put them in now by repeating steps 6
through 9.
If the PCI card you are installing is full-length,
then be sure that it fits in one of the three card
guides toward the front of the computer.
(back of computer)
147 Installing an Expansion Card