Doors often refer to the openings of the body and, therefore, by default, one’s sexuality.
The front door and back door signifies the vagina and the anus respectively. Breaking down such a door can be taken to indicate the need to deal with some kind of inhibition over privacy or sex; there can be an unwillingness to face whatever issues this may bring up. Barring the door highlights our need for self-protection, not just in matters of relationship. Opening and closing the door can show an ambivalent attitude to sex, whereas refusing to open the door represents an innocent approach to our own sexuality; we may have a virginal mentality.
A door between the outer and inner rooms shows there may be a conflict between the conscious and the unconscious.
If an animal or person forces his way in and destroys the lock, it shows our own protective mechanisms have let us down. Escaping by another door indicates we need to find a new solution to the one we originally thought of to solve a problem.
Someone knocking on the door signifies that our attention is being drawn to an external situation. You might like to consult the individual entry for door.