This document describes the different types of lines used in technical drawings and sketches, known as the "alphabet of lines". It explains that lines have specific meanings based on their thickness, shape, and dash pattern. Some key line types include object lines for visible surfaces, hidden lines for non-visible surfaces, center lines, dimension lines with numeric values, and leader lines to connect dimensions to drawing features. The document provides examples of different line styles and their uses in technical drawings.

1. Alphabet of
Lines

2. ALPHABET OF LINES
 Lines are the critical component of
sketching
 Lines have different types,
thickness and shape has its own
meaning
 Alphabet of Lines are also known as
“Line symbols”

6. OBJECT OR VISIBLE LINE
 Thick, dark line used to show the
outline of the object. Define
features you can see in a particular
view

7. CONSTRUCTION LINE
 Lines that are very light and very
thin use to construct layout work

8. DIMENSION LINE
 Thin and dark lines use to show the
size (span) of an object with a
numeric value. Usually terminates
with arrowheads or tick markings.

9. HIDDEN LINE
 Short dash lines use to show non visible
surfaces that are not visible in
orthographic view. Usually shows as
medium thickness.

10. CENTRE LINE
 Long and shot dash lines. Usually
indicates centre of holes, circles
and arcs. Line is thin and dark.

11. EXTENSION LINE
 A light line that extends from the edge
or end of a main object line on a
drawing, used in conjunction with
dimension lines to help determine
the dimension of a particular feature.

12. CUTTING PLANE LINE
 Extra thick line use to show
cutaway views or plane of
projection where a section view is
taken. Arrow indicates direction of
view.

13. LEADER LINE
 A thin line used to connect a
dimension line with a particular
area or point on the drawing. It is
also use to show notes or labels.

14. PHANTOM LINE
 Long line followed by two short
dashes use to show alternate
position of a moving part.

15. SHORT-BREAK LINE
 Thick wavy line that is used to
break the edge of a surface of a
part for clarity on a hidden surface

16. LONG-BREAK LINE
 Long, thin lines that is used to show
that the middle section of an object
has been removed so it can be
drawn on a smaller piece of paper