Parchment making was not a perfect process. Sometimes things would happen during it and leaves would come out with defects such as holes in the middle of leaves or a curved edge. Since parchment making was such an intense process these defect leaves couldn’t be thrown out. They were used and sometimes even repaired before use.

Holes in leaves are sometimes a result of a defect in the animal skin. If an animal had an injury or bug bite before it was killed than this wound would become part of the parchment. Holes from this type of defect are easy to find because they occur only in one place; whereas, if a bug had come through and eaten parts of a finished manuscript, then the hole would span several leaves deep into the text.

 Curved edges on leaves also could be a result of how the sheets were cut. For example if one side of the sheet was cut using a curved part of the skin such as the shoulders, then the sheet would obviously have the same curved edge.