Here is a simple trick how to cut a large piece of paper or cardboard into two perfectly symmetrical halves:
- Fold the paper. Make sure that the open side matches perfectly. Put some weights on them to keep them in place.
- Now sharpen the fold. Use a book or the handles of your scissors. It doesn’t have to be razor sharp, though.
- Cut the fold away with a knife or scissors.
It’s simple to make a straight cut when you only have to keep 1-2mm distance to the edge of the fold. Also, even if you’re completely inept, the two pieces will have the exact same width at the point where you started. If you need to glue them together, they will match perfectly.