A variety of line styles graphically represent physical objects. Types of lines include the following:
visible – are continuous lines used to depict edges directly visible from a particular angle.
hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views.
section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."
phantom - (not shown) are alternately long- and double short-dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. E.g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing.
Lines can also be classified by a letter classification in which each line is given a letter.
Type A lines show the outline of the feature of an object. They are the thickest lines on a drawing and done with a pencil softer than HB.
Type B lines are dimension lines and are used for dimension, projecting, extending, or leaders. A harder pencil should be used, such as a 2H.
Type C lines are used for breaks when the whole object is not shown. They are freehand drawn and only for short breaks. 2H pencil
Type D lines are similar to Type C, except they are zigzagged and only for longer breaks. 2H pencil
Type E lines indicate hidden outlines of internal features of an object. They are dotted lines. 2H pencil
Type F lines are Type F lines, except they are used for drawings in elector technology. 2H pencil
Type G lines are used for center lines. They are dotted lines, but a long line of 10–20 mm, then a gap, then a small line of 2 mm. 2H pencil
Type H lines are the same as Type G, except that every second long line is thicker. They indicate the cutting plane of an object. 2H pencil
Type K lines indicate the alternate positions of an object and the line taken by that object. They are drawn with a long line of 10–20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2H pencil.
