In heraldic achievements, the helmet or helm is situated above the shield and bears the torse and crest. The style of helmet displayed varies according to rank and social status, and these styles developed over time, in step with the development of actual military helmets. In some traditions, especially German and Nordic heraldry, two or three helmets (and sometimes more) may be used in a single achievement of arms, each representing a fief to which the bearer has a right. For this reason, the helmets and crests in German and Nordic arms are considered to be essential to the coat of arms and are never separated from it. Open-visored or barred helmets are typically reserved to the highest ranks of nobility, while lesser nobility and burghers typically assume closed helms. While these classifications remained relatively constant, the specific forms of all these helmets varied and evolved over time. In ecclesiastical heraldry, bishops and other clergy use a mitre or other rank-appropriate ecclesiastical hat in place of a helmet. History The evolution of heraldic helmet shaped followed the evolution of helmet design, especially jousting helmets, from the 14th to 16th centuries. The armorials of the second half of the 13th century do not include helmets. Helmets are shown as integral part of coats of in the first half of the 14th century (Codex Manesse, Zürich armorial). These helmets are still of the "great helm" type, without movable visor. Heraldic helmets become diversified with the development of dedicated jousting armour during the 15th and 16th century. The development is halted with the abandonment of jousting as a courtly practice, in the early years of the 17th century. From that period, the various types of heraldic helmet are purely driven by convention, and no longer tied to improvements or fashions in armoury. The practice of indicating rank through the display of barred or open-face helmets appears around 1615. As jousting with lances was supplanted by tourneying with maces, the object being to knock the opponent's crest off his helmet, the fully enclosed helmet gave way to helmets with enlarged visual openings with only a few bars to protect the face. These barred helmets were restricted by the imperial chancellery in Vienna to the nobility and certain doctors of law or theology, while the jousting helm was freely adopted by anyone. The direction a helmet faces and the number of bars on the grille