IBM 9080-M9S Manual page 490

Figure 421. Removing the side cover from the adapter cassette for the 9080-M9S system
4. Remove the top cover from the cassette.
a) Press the release button on the top cover and slide the cover in the direction that is shown.
b) Lift the top cover off the cassette.
484 Power Systems: Removing and replacing parts in the 9080-M9S system