supporting the wall
When you are out, but instead of enjoying yourself you proceed to lean against the wall, a pillar, etc. Usually with some alcoholic beverage and/or a cigarette.
Lisa: Oh my! I am having such a great time, are you alone here by the way?
John: Nah, my friend Paul came along, but he is only supporting the wall!
John: Nah, my friend Paul came along, but he is only supporting the wall!