Update on 2/10/2023: I added a different “Rastered” set that has only one registration ledge to accommodate people who may have situations where they cannot use the bottom ledge in the original design. These 3 new designs are the same profile curve as the others, but they've been rastered on the profile so they roughly center on the single registration ledge. I realized I needed one of these myself when I made a mistake drilling my wall, and made the whole set again for others. This one also features oval shaped holes on the Octagonal example to allow for a little slop in fits. Step file included.
I needed to put a mounting block and passthrough in my garage wall for an EV charger plug (as someone else did here).
Unfortunately, I couldn't find commercial mounting blocks that looked nice, or matched my vinyl profile, which is a standard 4-inch spacing lap (not dutch lap!). This type is pretty common on a lot of houses, but instead of the curved profile, I found lots of commercial solutions use generic triangles for alignment, which doesn't lead to good sealing and ends up having the blocks deform sometimes. They were also annoyingly expensive or unavailable.
So, I modeled a few new ones, including one for the insert used in project linked above (black insert you can buy here). I hope these are useful for others!
Modify to fit: