When a cylindrical tool cuts through a thin sheet of a relatively brittle material, it leaves behind a
visually arresting crack street in its wake, reminiscent of a vortex street in the wake of a cylinder
moving through a fluid. We show that simple geometrical arguments based on the interplay of in-plane
stretching and out-of-plane bending suffice to explain the cycloidal morphology of the curved crack.
The coupling between geometry and dynamics also allows us to explain the ‘‘stick-slip’’-like behavior
of tearing and suggests that these oscillations should occur generically in the brittle fracture of thin
solid films.