 Drawings are used to communicate ideas and concepts from the design team to the manufacturers, maintainers, and users of an item. One of the biggest challenges in communicating drawing concepts is the issue of perspective. An item in the real world is three-dimensional, yet the design team must communicate information about the item on a two-dimensional drawing. To avoid the distortions that occur when attempting to draw a three-dimensional item on a two-dimensional surface, designers have come up with a method called orthographic projection. In this method, each view is related by 90 degrees of separation. For example, the front view is rotated 90 degrees from the top. The top view is rotated 90 degrees from the side, and so on. The orthographic method shows each of the six main views of a three-dimensional object separately on a two-dimensional drawing. To obtain each of the views of an object, imagine that the object is within a glass box. Each side of the object gets projected onto the wall of the box. That projection is then shown as its own view on a two-dimensional drawing. The views are laid out in a pattern such that the top view will be located above the front, and the right side view will be located to the right of the front, and so on. This convention makes it easy to understand which view is shown and how it's related to the other views. If a drawing has only one view, it is the front view. Since a two-dimensional drawing can only convey height and width, information on the thickness of the item may be found in the notes or parts list. This is typical for items made from sheet or plate where the thickness is uniform and can be conveyed in writing so that a second view is not required. While every object can be illustrated in six views, only two views, 90 degrees apart, are required to illustrate an item in 3D. For complex parts, two views may not be enough to show all the critical details. In those cases, views are added until all the details are adequately conveyed. Users of drawings must be able to visualize from the two-dimensional illustrations how the three-dimensional part will look. Complex parts show much more detail on each view, but can ultimately still be illustrated in the same way. As with a simple part, imagine the complex part in a glass box. Each side projects an image onto the wall of the box. This image becomes one view. The three views normally shown using the orthographic method are the top, front, and right side. Objects are typically drawn so that the most complex view is the front view, even if this does not correspond to the front of the part. If the three views are not enough to show all the details required, additional views are added until sufficient detail is shown.