My ex is a carpenter/contractor, an excellant one I might add. But for reasons I won't go into I can't ask him. (no, he's not in jail) I have some questions I could use answered. Here's the first. I used a square to measure some wood to cut. Cut it. I needed to sand the edges a bit & when I was finished they were no longer square. The grinding/sanding attachment/shelf is both square & level. I checked it. I salvaged the pieces but they are smaller than what I really wanted. If this had been a paying job, or expensive wood, I'd have lost money. WHAT did I do wrong??