Epson EL 3S/33 - Manual (Page 68)

7. Slide the bracket toward the side of the computer until the
tabs hold the bracket secure.
8. Secure the mounting bracket with the screw, as shown
above.
Installing the Hard Disk On the Mounting Bracket
You can also install a hard disk drive on top of the mounting
bracket rather than under it. Refer to the illustration on
page 4-7 and the one below while following these steps:
1. Remove the screw securing the mounting bracket to the base
of the computer.
2. Slide the mounting bracket toward the diskette drive bays
until the slots clear the tabs.
Installing and Removing Drives 4-9