Building blocks for the shapes of confined elastic sheets

Several configurations, such as d-cones, minimal ridges, and developable patches, occur regularly in the configuration of elastic sheets. We dub such features ``building blocks.'' Here, we study elastic sheets confined in a manner that prohibits the sheet from taking on a single-buckle shape. We find not only building blocks where stress focuses, reminiscent of d-cones, but also ``diffuse-stress'' regions. The former is characterized by a geometrical constraint (inextensibility) while the latter is governed by a mechanical constraint: the dominance of a single component of the stress tensor. We characterize how boundary conditions and applied tension select which building blocks appear and discuss implications for the curtain problem.