CalDigit RAID Card - Manual (Page 9)

9 A. MacPro
1.4 Remove the drive modules
Make sure the latch on the back panel is open, and pull out all four drive
modules as well as their empty carriers.
1.5 Remove the PCI bracket
(Loosen the two thumbscrews on the bracket that holds the PCI Express
cards in place, and remove the bracket and the port access cover.
Port access cover
PCI bracket
Latch