Sentence:  For the occasion on which everyone already knows everyone else and the host wishes them to meet one or a few honored newcomers , then the `` open house '' system is advantageous because the honored guests are fixed connective points and the drifting guests make and break connections at the <WSD>door</WSD> . 
Meaning of the word marked with <WSD> tags:  the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close