I'm working on my son's 1990 Chevy k1500 with the 5.7 snd 4WD. I'm looking for help installing the two air vent retainers I ordered and received from LMC truck. For reference, LMC's item # is 31-1371. Supposedly, their purpose in life is to hold in (retain) the two air vents located in the in the top half of the deck trim. For refence please see the pic of the trim and the vents in question by clicking on the link below. If it works, it should take you to a random YouTube that shows the two vents. Without the retainers the vents fall inward. There are no holes in the baack of my trim piece to use to secure the ends of the retainers. So, I must be missing something obvious. Hope this makes sense and thanks for your help in advance.