Tandberg Data Storage Library T128 User Manual page 157

c. Open the module's access door and raise the guide pin by pulling it up and turning it slightly as
if it were a screw. Otherwise, the guide pin may scratch the front doors of the module on which
you are stacking it.
4 Lift the module, align it so that it is parallel with the module below it, and slide it into place.
5 Lower the module's guide pin by turning it and pushing it down.
Tandberg StorageLibrary T128 User's Guide 145