IBM RT User's Setup Manual page 159

1-8 Options Installation
7. Notice the location of the three tabs on the bottom of the
system unit.
8. To remove the front cover:
a. Push up on the tab until it is free from the hole in the
bottom of the unit.
b. Rotate the cover out, away from the bottom of the unit.
c. Lower the cover until the hooks are clear of the top of the
unit.
Left Cover Tabs
Front Cover Tab
AJZIF031
AJZIF032