Matrox Helios Series Installation And Hardware Reference page 31

5. If you are installing the I/O adapter board of Matrox Helios eA/XA in a
PCIe/PCI/PCI-X slot, align the board's tab with the slot's connector, and then
press the board firmly but carefully into the slot's connector. For other types of
slots or when installing the I/O adapter board of Matrox Helios eCL/XCL, slide
the board's bracket into the opening at the back of the selected slot.
6. Anchor the I/O adapter board's bracket to the chassis using the screw that you
removed in the previous section.
Installing an I/O adapter board 31