This network of enclosing slender stone bars is typical of the Perpendicular style. Indeed the style denies the solidity of stone walls. The style is epitomized in the great east end window which closes off the cathedral without a vestige of solid wall. The window is made with two new elements, transoms and mullions. They are a part of all Perpendicular window tracery.
Transoms are horizontal stone bars which cross the window at intervals.
Essential in the creation of large-scale windows, they provide both a framework for the glass and stiffening for the fragile tracery. Previously mullions had been turned into arches. In Gloucester the beautiful network of tracery bars covers a much older Norman choir, parts of which are still evident in the heavy masonry. The new work was initially conceived as a decorative overlay or disguise. Many great Perpendicular monuments evolved in this way.