Dell Inspiron 15 (3531, Mid 2014) - Manual (Page 22)

Procedure
1 Align the notch on the memory module with the tab on the memory-
module slot.
2 Slide the memory module into the slot at an angle and press the memory
module down until it clicks into place.
NOTE: If you do not hear the click, remove the memory module
and reinstall it.
1 tab 2 notch
3 memory module
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