Epson EL 486UC - Manual (Page 95)

2. If you are installing a drive with a card-edge connector, make
sure you align the key-way (the plastic divider) with the
gap in the drive connector, as shown below.
If you are installing a 3.5-inch diskette drive with a header
connector in the lower bay, see page 5-19 for instructions
on connecting this cable.
gap
k e y - w a y ,
3. Locate one of the power supply cables that lead from the
power supply. (They have multi-colored wires and a plastic
connector on the end .)
Installing and Removing Drives 5-17