Medieval Patterns

Many medieval books include beautiful, decorative patterns, some of which show an astonishing attention to detail. Patterns often appear as borders or as decoration around capital letters.

As borders

Blue border from 15th century manuscript
 
 
Yellow border from Book of Hours
 
 
Pattern created in Bruges between 1462 and 1467
 
 

Around Capitals

What are patterns? Where do we find them? How do patterns communicate to us?