From memory
My dad loves puzzles. He would do them when I was a kid, but he had a rule I’ve never heard of before. I’m not sure where or when he created the rule, but he was very strict about it for himself even though he never forced it on us.
He would study the picture intently before opening the box, but once the box was opened he would not look at the picture again. He would do the puzzle from memory.
To this day I don’t know why he did it this way. Maybe he wanted more of a challenge. Maybe he wanted to show off, or it was his version of a brain game.
No matter what his motive was, ever since I was a kid I always thought looking at the puzzle picture was a form of cheating. But I do it anyway.