A little dramatic, sure, but the name alone, right? So here it is :
It’s a tool for resizing while copying (including - of course - 1:1). Naturally.
Well, no. Not for me. I mean it kind of works:
As in, you can copy things. I guess I was trying something very small? However, why would I not just use tracing paper … except you can size up (or down). One to try again.