We present the X-Shell pavilion, a lightweight structure composed of elastic beam elements joined in a special layout that allows easy on-site deployment. The structure’s undeployed assembly configuration lies mostly flat and is easy to build, consisting of GFRP rods connected with mechanical fasteners made of aluminum and steel. The structure is deployed simply by either stretching the flat layout or by driving open the angles between rods at the joints. As the structure expands, the constraints imposed by the joints force its beams to bend and the whole structure buckles into its predetermined target shape. Unlike traditional gridshells, our structure does not require boundary supports to maintain its shape. Instead, the structure’s shape is directly encoded in the flat layout of its beams, their cross-section geometry, and material properties. The structure can be locked in its deployed configuration just by fixing a few joints. Apart from simplifying deployment, this feature offers several advantages. For instance, it allows the beam ends touching the ground to be mounted on castor wheels without the structure collapsing back into its flat state.