Some old books had feet

Erik Kwakkel explains:

When medieval binders knew that the object they were processing would be placed on a lectern, for example in a chained library, they often added tiny feet like the ones seen here. They made sure that the lower edge of the binding and the bottom part of the pages would not be damaged by the rough wood of the lectern - notice the shiny bottom of the feet.

More photos at the link, and more details here of a chained library