Yamaha MOTIF RACK ES Owner's Manual page 100

Optional Plug-in Board installation
5.
Carefully plug the cable connector into the Plug-in
Board connector until the two notches on the cable
connector lock into the sockets on the board as shown
in the illustration.
6.
Mount the Plug-in Board onto the plate as detailed in
the following steps.
6-1
Insert one side of the Plug-in Board (the connector side) into
hooks 1 as shown in the illustration, making sure that the
cable is above the board.
hook 1
100
Owner's Manual
Installing the Plug-in Board
hook 1
6-2
Press down the other side until it is securely settled on hooks
2.
6-3
Put the cable into the MOTIF-RACK ES, making sure that no
part of the cable sticks out of the instrument.
7.
Replace the Plug-in Board cover by fastening the six
flat-head screws you removed in step 2.
hook 2