need help installing roof racks

Hi, everyone, okay, I need some advice: I'm trying to install a set of factory roof racks, but I'm having difficulty trying to pry out those plastic thingies at the rear of the hold-down roof rails; no matter how I try, those things just won't pop off. Any suggestions? thanks!

i would check with the dealership parts department...call and tell them that you think you need those pieces, and say one is missing..bla blah blah...and what holds them on?