3

Understanding Line Types

3.1 INTRODUCTION—THE ALPHABET OF LINES.

The alphabet of lines is the universal language of the technician, architect, and engineer. In reality, lines are

the basis of all construction drawings. To read and understand blueprints, you need to understand the use

of lines. By combining lines of different thicknesses, types, and lengths, it is possible to graphically describe

objects in sufficient detail to allow a person with a basic understanding of blueprint reading to accurately vi-

sualize their size and shape. As will be explained, line characteristics such as width, breaks, and zigzags all

have meaning, and each line has a specific design and thickness that distinguishes it from other lines.

Drafting is an international graphic language that uses lines, symbols, and notes to describe a struc-

ture to be built, and lines themselves are expressive tools on well-executed drawings. Certain lines are

drawn thick so they stand out clearly from other information on the drawing, whereas other lines are

drawn thin. Thin lines are not necessarily less important than thick lines, but they are subordinate for

identification purposes. Drawings with only lines of the same intensity are often difficult to interpret and

usually monotonous to read.

As mentioned in Chapter 1, there are a number of organizations such as the American National

Standards Institute (ANSI) and the International Organization for Standardization (ISO) that have volun-

tarily adopted certain drafting standards that are generally accepted and widely used around the world.

3.2 LINE WEIGHTS AND TYPES.

Line weights are generally subject to the following conventions:

1. For manual pencil drafting using drawing boards, finished work includes bold object lines (2H to B
   pencils), light dimension lines, center lines, section lines, and so on (3H to 5H pencils). Temporary
   construction lines, guidelines for lettering, and other types should be kept very light (7H or 8H).
   Border lines for the drawing sheet and title block should be made bold (3B to 6B).


2. For inked or computer-plotted drawings different pen widths are used to achieve similar effects
   (see Figure 3.1). When plotting (printing) using a laser or inkjet printer from a computer drawing in

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