Why do FirePro graphics cards have those long black things at the end? (Plz no dirty minds)

[atomicwaveblast]

So if you look at some FirePro cards they have those blacks things at the end and basically, what are they?

Link for picture https://imgur.com/gallery/M9plO

 

[Mark RM]

It's designed to go into a slot at the far end of server and workstations that hold the card in place. Both ends are secured that way.