To damage

When it comes to creating a gypsum plasterboard ceiling with your own hands, this procedure is perhaps the simplest, and after the first sheet, you can learn to successfully mark and cut drywall sheets without problems. But in this process you can encounter complexity, sometimes you need to cut only three centimeters, and if you do it, just as you usually mark the ceiling from drywall with your own hands when cutting sheets, then the probability of a successful completion of the operation is almost zero. Therefore, in order not to damage the sheet itself, you need to mark and make the grooves (as deep as possible) on both sides of the sheet, and only then break, using the thumb as an stop.