Attaching lower door carpet panels
 

Last set of lower door panels I installed I drilled holes not knowing you can't drill loop carpeting. Kinda screwed them up. Someone on the forum suggested velcro. I've attached photos of the one I used. Very thin and pretty strong. I originally used it to put up a mirror frame for the wife. Works great.

Re: Attaching lower door carpet panels
 

Velcro could work.
But if you want to make neat holes in carpet first figure out the placement of the holes. What do is install the screws so I can feel them thru the carpet and then mark them on the carpet. Then using a small butane torch I heat up a small screw driver so it will melt thru the carpet. It will make a nice neat hole for the screws.

Re: Attaching lower door carpet panels
 

I use these. I do not know what they are called, but you take the thin round piece and it goes on the side of the carpet you see. You take the large round piece on the back side of the carpet, and push it over the 3 little pins, then bend the pins. You screw the snap screw into the door and the carpet snaps onto the door snap...if all of this makes sense.

You cannot see the thin round piece. I use this on all the carpet I install on the floor and walls if it needs something to hold it in place.