IBM 6648 - Manual (Page 71)

Cover removal
Firmly press the cover latch buttons on both sides. Pull up the back end of
cover, and swing the cover toward the front of the computer.
Note
The front panel is integrated with the top cover.
Replacing the cover
Position the cover over the chassis and pivot the cover down over the
computer until the cover snaps into place.
Chapter 2. Types 6568/6569/6648/6649 57