Epson Equity 320SX PLUS - Manual (Page 148)

2. There are two or three holes on each side of the disk
drive. When you insert the drive, align the appropriate
round holes in the drive with the two oval holes on each
side of the drive bay, as shown below.
3. Insert the drive in the lower drive bay and slide it toward
the back of the subassembly. Watch the oval holes on the
side of the drive bay so you can see when the holes on
the drive are positioned in the middle of them.
If you are installing a diskette drive, adjust its position so
that the front of the drive lines up with the drive in the
upper bay. (A hard disk drive fits all the way into the
bay.)
7-20 Installing and Removing Disk Drives