Apple Xserve (Early 2008) DIY Procedure for Enclosure - Manual (Page 163)

Xserve (Late 2006/Early 2008) Rear ID Tab Replacement Instructions 22
Holding the processor by three corners only, keep the processor level as you place it into its 7.
holder on the logic board, being careful not to get any thermal grease on the contacts of
either the processor or its socket holder.