2. Lines and lettering are basic elements of
technical drawing. Technical drawing is a universal
language of technology. Learning these elements
help you to read and interpret technical drawings and
plans correctly.
4. Freehand sketch- is such
a drawing which is drawn without
measuring instruments.
This drawing is drawn with the
help of pencil and eraser only.
5. Mechanical systems drawing
is a type of technical drawing that
shows information about heating,
ventilating, air conditioning and
transportation around the building
(Elevators or Lifts and Escalator). It
is a powerful tool that helps analyze
complex systems.
6. A line has length,
width, tone, and texture. It
may divide space, define a
form, describe contour, or
suggest direction.
7. Lettering is defined as the
process of adding letters such
as on a sign or the letters that
have been written. Can be
simply defined as “the art of
drawing letters”.
8. Alphabet of Lines
A List of line symbols is called the Alphabet of
Lines. Each line represents a meaning and purpose.
9. Alphabet of Lines
Type of Lines Appearance Description
Visible line Continuous thick line
Dimension line Continuous thin line with arrows or
Ticks at both ends
Extension lines Two thin lines
Leader line Thin line with a pointer
Hidden line _ _ _ _ _ _ _ _ _ Dash thick line
Center line ___ _ ___ _ ___ Chain thin line
10. Meaning of Lines
• Visible lines represent features that can be seen in the
current view.
• Hidden lines represent features that can not be seen in the
current view.
• Center line represents symmetry, path of motion, centers of
circles, axis of symmetrical parts.
11. • Dimension and extension lines indicates the sizes and
location of features on a drawing.
• Leader line it used for indicating the measurements and
name of a part.
