IBM 5155 Manual To Operations page 287

61
For each of the adapters just installed in the
expansion slots, align the slots in the adapter
retaining brackets with the hole in the rear panel
of the system unit. Insert the screw and tighten
with a flat-blade screwdriver or a S.S-mm
(7/32-in.) open-ended wrench.
Not
Properly
Aligned
Aligned
Option Installation 4-59