I came up with this in a Field Study course in which I took at group of students to NYC to study unions and workers centers. The students had no experience of unionism, so we needed to come up with a working definition of "union" so that we had a common basis for discussion. (As opposed to me just explaining what a union is, or given them someone else's definition. - What's wrong with explaining? Read on.) This activity gave us a great starting point for our discussion and it captured something essential about unionism and any social movement: the need to constantly reinvent and reimagine.