What I know and what I don't

In the last posts that I wrote, I was talking about repairing photos. At the moment, I am SO in the mood to repair my old photos or make them into a collage. If I read other posts talking about repairing photos, I still try to find out what kind of effects they use. BUT I don't have any idea, if people are talking about cad drawing. I remember my ex-colleague knows how to work with that :D