Engineering:Book clasp

Short description: Fastener for a book cover

Metal closure:
volume with alchemical treatises (tied in Strasbourg around 1568, collection of the Science History Institute, Philadelphia)

Leather closure:
Sachsenspiegel (hand written in 1385, Duisburg city library)

A book clasp is a leather or metal element attached to the medieval and early modern book covers, used to protect the book from the penetration of dust and light.