Miter lines are used to provide additional views of an object in drafting, where multiple views and angles are needed. The miter line shows a combination of the lines on the top view and right-side view, almost as if the piece were sliced open and spread out flat to be viewed.
These 45 degree lines help increase the accuracy of drawings and projects that will be turned into a three-dimensional object. This method also helps outline the right-side view of the object that is being designed. When using these lines, the drawing must be properly lined up or the measurements and production of the drafted item could be sized wrong.