IBM 5155 Manual To Operations page 325

3
Check to see that all of the pins on each module
are seated properly in the connectors and that all
the notches are facing the top of the option.
If
the modules are incorrectly installed, you can
remove the modules with a module puller, as
shown below.
j - o f - - -
Module Puller
Module
January 1984
64/256KB Memory Expansion 5