Asus M4A79T Deluxe/U3S6 - Manual (Page 28)

2-8 Chapter 2: Hardware information
Chapter 2
2. Attach one end of the retention bracket to the
retention module base.
3. Align the other end of the retention bracket to
the retention module base. A clicking sound
denotes that the retention bracket is in place.
4. Push down the retention bracket lock on the
retention mechanism to secure the heatsink
and fan to the module base.
Ensure that the fan and heatsink
assembly perfectly fits the retention
mechanism module base, otherwise
you cannot snap the retention bracket
in place.