Asus P5B-MX/WIFI-AP - Manual (Page 28)

1-16 Chapter 1: Product introduction
5. Rotate each fastener clockwise to
ensure correct orientation when
reinstalling.
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.
The narrow end of the
groove should point
outward after resetting.
(The photo shows the
groove shaded for
emphasis.)