Above: a medieval manuscript mended with embroidery. Photos via the Uppsala University Library. Here is some information about the manuscript from their page:
The pages of the book are made of parchment and they show typical damage in the form of holes and tears that happened while the parchment was being made. Some time after the book was copied, the holes and tears have been mended artistically with silk of various colours, mainly in blanket stitch as used in embroidery.
The old mending is in good shape except for those parts which were sewn with black silk. The thread is so fragile that it disintegrates on touch.
Read more here.