The summertop construction: Crystals in a corner

Equilibrium shapes of crystals in contact with more than one substrate, e.g., droplets at a corner or the edge of two planes, are described. This generalizes a construction due to Wulff and Winterbottom and, unlike them, allows non-convex equilibrium shapes. Since this construction may require a central inversion of the Wulff plot, it is dubbed “the summertop construction.”