Mullion

In Gothic architecture, windows became larger and arrangements of multiple mullions and openings were used, both for structure and ornament.

This is particularly the case in Gothic cathedrals and churches where stained glass was set in lead and ferramenta between the stone mullions.

[3] I. M. Pei used all-glass mullions in his design of JFK Airport's Terminal 6 (National Airlines Sundrome), unprecedented at the time.

Also in the case of a curtain wall screen the weight of glazing can be supported from above (providing the structure can take the required loads) this puts the mullions under tension rather than compression.

In traditional designs today, mullions and transoms are normally used in combination with divided-light windows and doors when glazing porches or other large areas.