This is the coolest tool I've had in a long time. It is a pattern notcher. Notches on a pattern tell you where to line up the edges of the pattern pieces, so you can get them to fit together correctly. This little punch tool make the notches simple to make on a home made pattern. It also makes the home made brown paper pattern look so professional just by the merit of having lovely, even and accurate notches!
It was a birthday present. I'm thrilled. It was one of the most thoughtful, extremely useful and fun gifts I've received in ages. I've already tried it out :) It is totally something I would have never bought for myself.