This article returns to what was once an ethnographic staple in the sociology of India: the post-harvest grain heap. Having long occupied centre stage in analyses of a moneyless, redistributive transactional order widely known as the jajmani system, it has also been the subject of influential critique, where it has been argued that the misconceived heap sustained a powerful anthropological fiction. Moving beyond these positions, which seem to have left the heap grounded in the past, the grain heap in this work is reconceptualised as a critical entry point and analytic for the study of contemporary commodity markets. Based on long-term ethnographic fieldwork in an agricultural market (mandi) in Madhya Pradesh, it finds that it is along the seams or internal margins of the market, at routine sites of physical transfer and exchange, assembly and dispersal, integration and disruption, that heaps of agricultural produce materialise. An analysis of critical aspects of the heap—its position, composition, measurement and distribution—provides sharp insights into the changing dynamics of the market and its complex relationships. In the process, it also reveals important yet often unnoticed shifts in the sources and distribution of economic and social margins, and their diverse and differentiated effects on market life and livelihoods. © 2018, © 2018 SAGE Publications.