Epson EQUITY 386/33 PLUS - Manual (Page 110)

The interface that protrudes from the back of the drive has
gold contacts on both sides. Align the connector with the
interface so that the plastic divider on the connector lines
up with the gap in the interface, as shown below.
Make sure the cable connector fits properly onto the drive
interface and then push it onto the interface. Then go to
step 8.
Caution
If you do not align the connector correctly, you could
severely damage your diskette drive when you push it in.
5-22 installing and Removing Drives