IBM 9080-M9S Manual page 614

Figure 530. Lowering the new system backplane into the rails
c) When the rear guide pins make contact with the slide rail mounting slots, slide the system
backplane towards the rear approximately 6 mm (.25 in) to align the middle and front guide pins.
d) As you continue lowering the front of the system backplane into the rails, the middle and front
guide pins drop into the slide rail slots.
You might find it helpful to hold the slide rails tightly against the system backplane so that the
pins will be seated flush with the rail slots.
5. Replace the chassis.
a) Lower the chassis straight down over the system backplane.
608 Power Systems: Removing and replacing parts in the 9080-M9S system