Epson LQ-860 User Manual page 186

2. Use the CG screw to attach the round end of the FG wire to the
main board and position the other end as shown.
3. Align the interface board with the CN2 connector on the main
board and with the interface port on the back of the printer.
Carefully insert the pins on the optional interface board into the
mating connector on the main board. Then secure the board with
three of the screws provided.
Using the Printer Options 5-49