We cannot survive without windows and doors.  That is one fundamental factor of today’s busy lifestyles.  In the very seriusly old days, families congregated in mud huts and hovels carved out caves and hillsides.   Gradually the need for long term adequate housing became more obviously customer led.   Usually a wooden framework, like an A frame for example, would be erected and many dozens of wooden support beams would be built in, with wattle & daub panels to spread the load.  There would be a hole in the very top of the of the structure to let out the smoke from the fire that was always in the centre of the room.   This was the main way of living unti an enterprising soul discovered the joy of window and door frames to let in light and let out the smoke and stench.  Gosh how things have improved – we have wonderful glass and many designs of framework to choose from.  Our ancestors would not believe their eyes if they could see the luxury we enjoy today!