Dell POWEREDGE M915 - Manual (Page 277)

Installing Blade Components 277
NOTE: If you are removing multiple mezzanine cards, label them so that you can
replace them in their original locations.
9 To remove a full-height blade system board:
a Use the thumb and index fingers of your right hand to lift the system
board retention pin. See Figure 3-61.
b Keeping the retention pin raised with your index finger, press the
corner of the blade chassis with your thumb to slide the system board
out of the open end of the chassis.