HP DL740 - ProLiant - 4 GB RAM User Manual page 148

HP has designed a self-latching slot-keeper feature to accommodate
full-length expansion boards.
Be sure that the V-shaped slot-keeper tabs on the plastic expansion board guide
are positioned over the forward end of the expansion board. Using the slot-
keepers is especially important when expansion boards are added or when the
server is moved.
Figure 5-23: Full-length self-latching slot-keeper feature
8. Properly connect the expansion board I/O cable.
HP ProLiant DL740 Server User Guide
Installing Hardware Options, Hot-Plug
5-49