This guide represents a complete overview of the design and protection issues for structures built on dikes, such as spillways. This chapter presents the civil engineering of these constructions. It introduces successively the safety criteria of spillways on dikes, the principle of a fusible or mobile raise, the shape in plan of spillways on dikes, the types of rectilinear sills and constituent materials, fusible or mobile raises, the continuity of maintenance tracks, a return on erosion by overflow on earthen dikes.