As part of a larger project on effective numeracy teaching practice a number of teachers took turns to teach a small group of students in front of their peers who were located on the other side of a one-way window. Observing teachers were asked to comment on what they noticed "in-the-moment" and suggest labels or metaphors that captured the essence of the teacher's acts to support learning. Twelve scaffolding practices were identified as a result of this activity suggesting that it is a valuable tool for making explicit what teachers know and exercise intuitively in the context of primary mathematics classrooms. Here, we describe the activity and illustrate its potential for building a meaningful, accessible language that teachers can use to actively reflect on their practice. [For complete proceedings, see ED489597.]