Casio WK-3700 Service Manual page 17

9. Remove 24 screws and then the PCB ASSY (KY1M, KY2M).
10.Remove the rubber keys.
Projection
Note: Pay attention to the positions of the rubber keys as one of them has a different length.
Match the projections of the rubber keys with the holes of the lower case when reassembling.
— 15 —