We noticed that when workers try to explain their mathematical practices to inquisitive outsiders, breakdowns in communication arise. We present here an example in which a worker spontaneously uses metaphors and models to facilitate explanation and communication. We analyse these, drawing on Lakoff & Johnson (1999) and Lakoff & Nunez (2000) in substance and theoretical approach. We suggest that metaphors and cultural models ground associations between academic and workplace discourse genres, and point out how sensori-motor groundings of the "basic" metaphors may afford gesture and image-schema which free discourse from formal mathematical language. In general we see breakdown repairs as being built through cultural models that extend beyond local mathematical genres which situate mathematics within academic or workplace contexts. [For complete proceedings, see ED489597.]