The outside edges of boards usually were square until the 13th century; after that time, they were often beveled, sometimes steeply, or, in the case of decorated bindings, on a more gentle slope. The inside edges were also frequently beveled during the 15th century, particularly in Germany.
When the outer edges of boards are beveled the edge along the spine is also often beveled on the inside, so that it follows the swelling of the spine. (58 , 236 )