Hat-sections are often used to experimentally investigate building sheeting subject to a concentrated load and bending. In car doors, hat-sections are used for side-impact protection. Their crushing behaviour can partly be explained by only observing their cross-sectional behaviour . This crushing behaviour includes the initial and progressive location of moving yield lines and will be explained in this article by an analytical model. The model predicts the results of finite element simulations  well, and gives good insight in the complex cross-section crushing behaviour of hat-sections.