To neatly fold the parts along the fold lines, as well as draw along the fold lines with a blunt object, a regular ruler will help you. Why metal? Because they are very thin, and it is very easy to bend parts with it.
If you have any line at home, there is no need to purchase it.
There are no special requirements for the rulers, the main thing is that they are dense (unbending, or you know, there are such anti-stress rulers that can be bent).
We recommend using a regular ballpoint pen with out of ink as an object that can be drawn along fold lines.
