Samsung CLP 550 - Manual (Page 263)

I NSTALLING P RINTER O PTIONS F.5
F
9 Push it firmly to make sure you fully insert the memory
DIMM into the slot. The levers on each side are
automatically latched.
N OTE : If you have difficulty inserting the memory DIMM or
closing the levers, make sure the notches on the bottom of the
DIMM are aligned with the notches in the DIMM slot.
10 Replace the metal cover, as shown below, and tighten the
two screws you removed in step 3.