Apple Mac Performa 640 series - Manual (Page 156)

4 Slip the three hooks at the base of the back panel into the grooves in the computer case.
5 Swing the back panel up and snap it into place.
6 Plug the cables back into the computer.
7 Reconnect the power cord.
Your computer is now ready to turn on 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.
Snap the plastic back panel into place.
Slip the three hooks on the back panel
into the grooves in the computer case.
148 Appendix B