Apple Macintosh Performa 6100 Series - Manual (Page 103)

7 Attach the card to the adapter card assembly.
Rest the adapter card assembly on the edge of a flat surface, with the metal
bracket pointing up.
Slide the NuBus card into the bracket. The pin on the bracket should line up
with the hole on the metal end of the card.
Press gently on the cards to push the connectors together.
When the cards are attached correctly, the pin fits in the hole and the guide
fits in the slot, as shown in the illustration.
Pin in hole
Guide in slot
93 Installing an Expansion Card