NEC Express5800 series User Manual page 169

Push the CPU lightly to the socket, and push down the lever to secure the CPU.
8.
Put the heat sink on CPU.
9.
NOTE: Be aware of direction of heat sink (see figure below).
Install the both heat sink clips as follows:
10.
(1) Hook one end of the clip over the tab on the retention.
(2) Align the clip with the slot in the heat sink and press down on the center of the
clip until it snaps over the center tab.
(3) Snap the remaining end of the clip down over its tab.
The bracket-attached side must be engaged with the rear of the socket.
Upgrading Your NEC Storage 159