Apple iMac (21.5-inch and 27-inch, Mid 2011) - Manual (Page 43)

43 Chapter 3 Boost Your Memory
11 Replace the memory access door and tighten the three captive screws with a
Phillips #2 screwdriver.
WARNING: Remember to replace the memory access door after you install memory.
Your iMac won’t function properly without the memory access door.
Phillips
screwdriver
Raise
stand
Memory
access
door
®
12 Hold your iMac by its sides and return it to a standing position. Then reconnect the
cables and power cord.
13 Press the power button (®) on the back of your iMac to turn it on.