This one comes from the Flite Test web site. If you build models from foam board eventually you will need to do a 50% score cut. A score cut will allow you to make a cut, then fold the foam board back on itself. You don’t want to cut all the way through. The tip from Flite Test is to take your cutting tool and round off the tip. Use whatever method you prefer. A couple choices are, a brick, sandpaper, or a file.