Acer AT350 F1 - Manual (Page 54)

3 System upgrades 42
5 Remove the four screws (1) that attach the metal brackets to the
empty 5.25-inch drive cage. Detach the metal brackets (2).
6 Align the metal brackets with the new storage device and make
sure the arrow (1) is pointing to the front. Align the notches on
the brackets with the holes (2) on the device.
7 Use four screws to secure the metal brackets to the new 5.25-inch
storage device.