The paper considers the primary types of defensive structures built in the Middle Ages from wood and earth, as well as the methods used for their construction. The author identifies an entire complex of construction methods based on centuries of experience and complex engineering calculations. The medieval wood and earth fortification sites are characterized by several types of vaulted wooden structures, such as log houses, pillar structures, picket fences or hedges, and a frame in the form of a horizontal wooden grating. In certain cases, the contemporary rampart earthwork can represent the remains of a collapsed log fortress wall with an internal backfill on the ground surface. The article considers the specific rampart filling techniques, alternation and mutual arrangement of embankments consisting of homogeneous or heterogeneous soil composition, additional reinforcement of the slopes of ramparts and moats, and draws attention to the shape deliberately rendered thereto. Defensive moats were an indispensable element in the system of military engineering structures in medieval states, and were represented by several types. There are fortified settlements with various types of moats, and combinations thereof in a single settlement. The author concludes that the variety of forms and types of these structures designed for not only passive, but also active defence, testifies to their special selection and application for each specific case, which primarily depended on the location of the fortified settlement and the area it occupied.