EXFO FTB-2 - Manual (Page 41)

Getting Started with Your Unit
FTB-2 and FTB-2 Pro 31
Inserting and Removing Test Modules
8. Position the unit so that its right panel is facing you.
9. Insert a locking screw in one of the screw holes on the front of the unit.
I
MPORTANT
EXFO recommends that you use the front locking screws to secure
the modules in your unit, especially when you work with heavier
modules such as the OSA, or the FTB-88100NGE PowerBlazer.
Screw holes