IBM RT PC Options Installation page 23

7. Notice the location of the three tabs on the bottom of the system unit.
Left Cover Tabs
8. To remove the front cover:
1-8 Options Installation
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.
a