Fujitsu PRIMERGY TX2550 M5 Upgrade And Maintenance Manual page 407

Main memory
Figure 262: Installing a memory dummy module - variant 1
Figure 263: Installing a memory dummy module - variant 2
▶ Align the notch on the bottom of the module with the crossbar in the slot.
▶ Press down on the dummy module until the securing clips snap into the
cutouts at each end of the module.
TX2550 M5 Upgrade and Maintenance Manual 407