I have used these on my 100w 12v Renogy panels for mounting on a curved RV roof. They line up at pre-made holes. I used blue thread lock on the screws holding the plate mounts. I also replaced the included screws; They came with 1.5 inch tapping screws. That's too long for an RV roof, also self-tapping screws aren't recommended for wood (they'll cut the tree you're trying to fall into). So I replaced 3/4 stainless steel screws (not self-drilling). Installation was easy and hassle-free. Fasteners are aluminum so no worries about rust or erosion. All sealed with dicor self-leveling sealant.