Asus AP1720-E2 - Manual (Page 82)

Chapter 3: Installation options 3-6
3. Make sure that the drive cage is
fits snugly to the bay as shown.
The drive cage is properly
installed when it is parallel to the
front panel, and the screw hole
matches the hole of the first drive
cage.
Screw hole
4. Secure the drive cage with a
screw.