Some HP metal chassis frames (Slimline s5000, s5-1000, 400-034, Envy 700, etc.) have cutouts under the front bezel and on the back panel where a WiFi antenna can be attached with a 6-32 screw (or slots to support antenna).
This option permits Wireless LAN (and Bluetooth) support without external antennas (Laptop, Tablet like).
This is a nice upgrade -- when the motherboard installed supports Wi-Fi option (adapter cards).
There are TWO different HP part numbers for the Wi-Fi antenna cover, on the desktop case rear panels. The part number, noted in earlier post, was for earlier HP cases (Pavilion Slimline s5000 series). The cutouts in the sheet metal (rear panel) are different, for these two covers.
The newer HP desktop cases (Envy, Pavilion) such as the Slimline 400-034 ; Pavilion 500-205t ; s5-1000 and p7-1000 series use this newer part.