Dell Latitude C840 - Manual (Page 11)

Memory Module and Modem Cover — Protects the memory module(s) and modem daughter card. See " Adding and Replacing Parts ."
Device Release Latches — Press a release latch to remove a device in the module bay. See " Using the Module Bay " for instructions.
Mini PCI card cover — Protects the optional Mini PCI card. See " Adding and Replacing Parts ."
Docking Device Latch — Latches onto the docking device.
1 memory module and modem cover
2 device release latches
3 Mini PCI card cover
4 docking device latch