Reticula and Fragments were introduced by Rick Roberts and Maria Thomas (founders of Zentangle) in their book Zentangle Primer Volume 1. Reticula are simply frameworks in which to place pattern fra… Doodle Designs, Doodle Patterns, Zentangle Patterns, Mandala Pattern, Tangle Doodle, Zen Doodle, Doodle Art, Zantangle Art, Zen Art