ASROCK H67M User Manual page 16

The DIMM only fi ts in one correct orientation. It will cause permanent
damage to the motherboard and the DIMM if you force the DIMM into the slot
at incorrect orientation.
Step 3. Firmly insert the DIMM into the slot until the retaining clips at both ends
fully snap back in place and the DIMM is properly seated.
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ASRock H67M Motherboard