>> What exactly are on these notes that's worth saving?
One example I gave above was swapping a brake caliper on a car. I'd sworn off that sort of thing but my mechanic was on vacation so I went ahead. Which meant re-learning everything from the last time, like ten years ago.
I buried some wires in the wall in my kitchen. It's against code but not much choice, splicing into existing wiring. So I used metal boxes so nobody drills into it, and took pictures with tape meaures showing where they are. I also remember, but not to the nearest inch.
Someone just asked about vertical dropouts and an IGH hub. I did this in 2008, and got a spreadsheet of the web that helped tremendously in figuring it out. It wasn't 100% but it was close, and it was spot-on when going from one chainring/cog combination to another. I don't have it anymore.
At least I found the order from where I bought spokes for a wheel I built a few years back, and the spokes are now breaking. My LBS rebuilt it and saw nothing wrong, still breaking. So I'm going to redo with new spokes from a different manufacturer. So I knew what length to order without measuring.
Stuff like that.
cheers -mathias