Focussing on teachers' subject pedagogical actions over the course of a series of lessons on a mathematical topic, this paper sets out an original analytical approach to characterise the shape of mathematics teaching decisions made over time: tri-polar analysis. The notion of manifestation is introduced as a way of categorising how the teacher is observed making content available to learners and the analysis explores sequencing and differences in emphasis of these categories across a lesson series. These differences are presented graphically and the implications for doing so in terms of opportunities for teachers' professional learning are discussed. The analytical approach is exemplified through the case of Ashley. Prominent between-lesson differences are discerned that suggest systematic variation in what is emphasised across the lesson series, consistent with deliberate and planned decision-making. But subtler between-lesson differences are also revealed through the analysis associated with in-flight decision-making.