Ortho literally means ‘right angle’. Orthographic projection refers to the transfer of images created by perpendicular projector rays, these rays are always parallel to each other.
All three principal planes are perpendicular to one another. Each two-dimensional principal plane can be classified as a picture lane because it records a picture image of the object.
The folding plane line is the intersection of any two principal planes. Imagine a transparent glass box containing the model, when opened on its hinges or folding plane lines it will become a two-dimensional surface. The plan and profile elevation planes are rotated to become a part of the frontal elevation plane’s extension.
Orthographic drawings are true-size and true-shape views that are related on a two-dimensional surface. When two planes are perpendicular to a third plane, any point in space (A) will be seen twice an equal distance (K) behind the third plane where (K) can be any distance.
In constructing related orthographic views use a 45° diagonal line from the intersection of the folding plane lines.