Beer-nails

College students have loved beer for centuries. They are also generally very smart. In one fit of brilliance, students invented biernagels (beer-nails).

These are metal studs placed on the covers of books to keep the leather covers away from wet (spilled beer) pub tables. With biernagels on it, a book cover is raised half a centimeter from the surface of the table, and thus remains mostly dry. From the name, we can only assume it was some inventive German students.