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.

Why I made this

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!

Check for fit with a test piece

• You can use the included test-piece to print the profile out and match it against your house vinyl to make sure the fit is pretty close.
• It's unlikely that you'll get a perfect fit in most cases, and be prepared to use a little clear exterior silicone sealant around the edges to make sure it's water-tight.

Choose which variant you want:

• I've included 3 variants here. Octagonal, Square, and an Octagonal with holes for the EV project linked at top.
• The regular octagonal and square ones come with a little centered dimple and 5 mm thickness for a portion of the mounting block to reduce material waste and show where the expected “drill through” area is.

How to print :

• If you're going to use this outdoors, choose a good weatherproof filament like PETG or ASA, or paint something less UV-resistant like ABS if you want.
• Use an appropriate amount of infill/perimeters and bottom/top layers for your needs. Since these are semi-structural and might be cut through, I recommend at least 4 perimeters, and 30-50% infill (i used gyroid).

Modify to fit:

• I've included a STEP file for people who want to model their own holes instead of drilling them in the blanks provided.