NEC Express5800/120Rd-2 Service Manual page 277

The wire clip is already installed on the heat sink at purchase. If it comes off, install it as
shown in the figure below.
NOTE: Make sure of the orientation of the wire clip.
Engage the wire clip with the socket.
8.
The bracket-attached side must be engaged with the rear of the socket.
Disassembly and Reassembly 7-33
Bracket attached to
the wire clip
Groove in the heat sink