Epson Progression U12 - Manual (Page 101)

3. The enhanced daughterboard has four sockets which fit over
the four pin connectors on the main system board. To
install it, guide the board into the computer so the interface
port extends through the opening in the back panel. Then
align the daughterboard’s four sockets over the pin
connectors on the main system board, as shown below.
Caution
Be sure to carefully align the holes in the sockets over the
connector pins on the main system board. If you install
the daughterboard in the wrong position, you could
permanently damage it and destroy the components on
the main system board.
3-32 Installing and Removing Options