The doorway in film offers a somewhat entry to a different environment or reality, as you enter the door way you are transported into a new area, the character may be somewhat vulnerable to the world that he or see had just entered. Without doors in film it is highly unlikely that the narrative can progress, as the character cannot enter a new realm that differs from the one they are used to in the first act of the narrative structure.
A most common use of doors to create major narrative progression is seen in the 2005 film Narnia the door to the wardrobe offers an entry into another plain of existence that differentiates itself from the reality that the protagonists exist in. Without the existence of this doorway the narrative would come to a halt and the land of Narnia would not have been discovered
The door can act as a threshold or a portal in a sense, this is not only present in cinema, today I was playing a game called Dark Souls in which the character struggling pushed two heavy doors open in order to reach the next level, moving from one space to another.
Doors also are a means of protection, a closed door can seal off the other side of the so called portal which may contain danger or a foreign world. Take The shinning (1980) for example, the famous door scene in which the door acts as protection from the axe wielding maniac yet as it is pierced through the symbol of danger becomes more evident to the female character.
The door may be interpreted in several ways yet I believe it symbolises the entry and exit between two different realms, weather it may be from location to location or from safety to danger. The door will always remain one of the most common and important symbols within cinema and screen.
liammccosh 