IBM Power Systems 9009-41A Manual page 103

Figure 88. Reconnecting the power cable and signal cable to the disk drive backplane
g) The chassis has two alignment pins and several brackets (A) to secure the disk drive backplane.
Using the thumbscrews (B), (C), and the alignment pins (A), insert the disk drive backplane as
shown in the following figure, while you ensure that the alignment pins fit through the holes in the
backplane.
Slide the disk drive backplane to the side in the direction that is shown so that the backplane
cutouts slide under tabs in the chassis.
Removing and replacing the system backplane in the 9009-41A, 9009-42A, or 9223-42H 89