Asus P5LD2-X/GBL - Manual (Page 34)

2-12 Chapter 2: Hardware information
5. Rotate each fastener clockwise to
ensure correct orientation when
reinstalling.
The narrow end of the groove
should point outward after
resetting. (The photo shows the
groove shaded for emphasis.)
Narrow end of the groove
Refer to the documentation in the boxed or stand-alone CPU fan package for
detailed information on CPU fan installation.