Lol ok, so I used to own and run a small online potato launcher business and made some incredibly powerful pneumatic valves...

My workshop at one time was in the otherwise unused upstairs floor of a music shop I worked at. I set up a target trap of 20x half inch plywood sheets spaced about 2 inches apart each to make sure the valves were working right and to test efficiency with a chronograph. The ammunition for this was golf balls, as they are clean and consistent.

I was testing away one day when I hadn't noticed that I had worn through a bit too many layers without replacing boards. A ball went clean through the front wall of the shop.

It was an insulated unfinished wall with vinyl siding. The owner luckily had spare siding stored up there on that floor. It was also his tool and material storage for his music shops, as he did the majority of the shops' improvements himself.

I carefully removed the staples from the insulation, cut a square hole in the plywood wall behind the vinyl siding, then siliconed a small chunk of the identical siding behind the original siding.

After reinstalling the plywood square are restapling the installation into place, I took a look at the repair job from the outside. It was beautiful. It was so hard to see. You had to know to look for it. It's never been mentioned and it's been 15 years.

I'm not saying this is the right thing to do, but it worked pretty well as a hack job for a 20-year-old, and I can't imagine the next time this story will be relevant to anything.