o he means the bottom plates at the bottom that can be taken out like pci slots. to be honest man i think its for wireless antennas or a hdd extension. my hp has a external thing like that for media attachments. or you can put another cooler of some sort. remember hp uses alot of the same cases for different builds.
The wireless card is installed, and the blower fan must install where the pci slot in order to install the metal end like when you install a video card