In the early Middle Ages, books were made from animal hides known as parchment, rather than from paper. Preparing the parchment was a delicate business. The freshly skinned hide is first washed to remove blood and grime, and then soaked in a strong alkali solution to loosen out the hairs. After staying in the de-hairing solution for more than a week, the skin is attached to a wooden frame and stretched tight like a drum. While the skin is drying, the parchment maker would take a sharp knife and scrap the skin to remove the last of the hair and get the skin to the right thickness. This was the most delicate part. Too much pressure during the scrapping process or a slip of the knife could leave elongated rips or holes on the parchment.