IBM Power System System E950 Manual page 28

Figure 9. Installing an adapter in the cassette for the 9040-MR9 system
9. Slide the PCIe cassette into the slot by completing the following steps:
Attention:
Ensure proper alignment when you insert a PCI adapter cassette into the system.
a) Align the cassette on the cassette rail in the cassette slot.
b) Slide the cassette forward until the cassette is fully seated.
c) To lock the cassette in its slot, squeeze the latch lever (A) toward the latch (B) and rotate the latch
(B) in the direction that is shown.
14 Power Systems: PCIe adapters for the 9040-MR9