Apple PowerBook (Duo 270C) - Manual (Page 251)

15. Replace the NuBus card guide by sliding it back into
position.
Your card is now installed.
16. Turn over the subassembly and carefully put it back
into the base of the dock.
17. Push the subassembly toward the back of the dock to
close the gap (the reverse of step 6).
continues .
Gap
Chapter 13: Building a PowerBook Duo System 235