Apple PowerBook Duo Dock (including Duo Dock Plus) - Manual (Page 45)

21 Replace the dock cover.
Align the cover over the base so that the corners align with the back edge of
the base. Press down firmly on the rear corners and then press down on the
front corners until the latches click.
See the information that came with your NuBus card for information about its
accompanying software (if any) and use.
WARNING Never turn on your computer unless all of its internal and
external parts are in place. Operating the computer when it is open or
missing parts can be dangerous, and can damage your computer.
39 Installing a NuBus Card