Apple Power Macintosh 4400 - Manual (Page 167)

Closing the computer
1 Slip the base of the logic board into the guide rails inside the computer’s case.
2 Reinsert the three cover screws you removed earlier.
3 Plug the cables back into the computer.
Reinstall these three screws.
Set the top cover down so there’s about a quarter of an inch gap here.
Then slide the top cover all the way forward.
167 Installing Expansion Cards and Additional Memory