For the new profile Trex boards (and possibly others) this template helps you mark for the correct screw or pre-drill location

I used PETG since this is going to be left in the hot sun and I don't want it to warp

Also included are some spacers for when you can't use the between board clips.
The hole in the spacer allows you to put a screw in (twist in by hand) to aid in pulling a spacer out