can somebody tell me how these are held to the hood? they have little plastic tabs on one side but nothing on the other. are there supposed to be some clips that hold these on?

 

Not sure how to get em off, but when mine were knocked off by a falling branch in a storm, I just snapped them back on. So, yes, they are held on by metal clips built into the vent that hook onto the metal of the hood. Sorry, not much info, but hope it helps...
~chris

 

they are shaped like little nuts but they dont have threads, and they just kind iof cut threads onto the plastic when you put them on, go to any local auto zone or something and show them your heat extractors and they will show you what you need