IBM 9080-M9S Manual page 445

Figure 377. Removing the top cover from the adapter cassette for the 9080-M9S system
7. Remove the tailstock filler from the cassette.
a) Pull the tailstock filler away from the cassette in the direction that is shown.
b) Save the tailstock filler for a future use.
You must have a tailstock filler in an empty cassette in a system to ensure proper airflow.
PCIe adapters 439