How to score card board so that the edge of your custom made box is perfectly square. So simple! Let me show you. 1. You need a metal ruler, and a stanley/box knife (I use this rather than a scoring tool because I’m using the knife to cut the board as I’m working - it’s me being lazy)2. Line the ruler up along where you want the inside of the fold to be.3. Press down really hard to hold to ruler in place so that while you score the board you won’t move it.4. Score the card by pushing the retract