Tracery is the term for the intricate designs of slender stone bars and ribs which were used to support the glass and to decorate rose windows and other windows and openings.
It also was used increasingly on exterior and interior walls, in the form of stone ribs or molding, to create increasingly intricate forms such as blind arcades.
This form was called blind tracery.

The west window of Chartres Cathedral used an early form called plate tracery, a geometric pattern of openings in the stonework filled with glass.
Prior to 1230, the builders of Reims Cathedral used a more sophisticated form, called bar tracery, in the apse chapel.
This was a pattern of cusped circles, made with thin pointed bars of stone projecting inward.
This model was followed and developed in the transept windows of Chartres Cathedral, at Amiens Cathedral and the other High Gothic cathedrals.
After the middle of the 13th century, the windows began to be decorated with even larger and complex designs, resembling light shining outwards, which gave the name to the Rayonnant style.
Tracery is the term for the intricate designs of slender stone bars and ribs which were used to support the glass and to decorate rose windows and other windows and openings. It also was used increasingly on exterior and interior walls, in the form of stone ribs or molding, to create increasingly intricate forms such as blind arcades. This form was called blind tracery.
The west window of Chartres Cathedral used an early form called plate tracery, a geometric pattern of openings in the stonework filled with glass. Prior to 1230, the builders of Reims Cathedral used a more sophisticated form, called bar tracery, in the apse chapel. This was a pattern of cusped circles, made with thin pointed bars of stone projecting inward. This model was followed and developed in the transept windows of Chartres Cathedral, at Amiens Cathedral and the other High Gothic cathedrals. After the middle of the 13th century, the windows began to be decorated with even larger and complex designs, resembling light shining outwards, which gave the name to the Rayonnant style.
High Gothic