162 Exploring Drafting
Orthogonal mode simplifies the task of
drawing horizontal and vertical lines. When
orthogonal mode is enabled, the movement of
thecursorisconfinedtohorizontalandvertical
movement on the drawing plane. Inclined
lines cannot be drawn when using this mode.
Orthogonal mode is useful for drawing lines
at 90° angles, such as the outlines making up
a drawing border.
Layers and Linetypes
In manual drafting, it is common to have
several different views or plans on sepa-
rate sheets for complex drawings, such as
mechanical parts with section views or archi-
tectural plans for a building. When this is the
case, the sheets are overlaid on top of each other
so that the different drawings can be viewed
separately. In CAD drafting, drawings can be
managed in a similar way through the use of
layers. Layers are user-defined object settings
that can be displayed or “turned off” to distin-
guish the differenttypesofcontentinadrawing.
See Figure 7-11. Using layers, several different
displays can be shown within a single drawing
fi le. It is very common, for example, to create fi
separate layers for object lines, construction
lines, section lines, text, and dimensions. The
display of each layer can be turned on or off
as desired. In this way, certain portions of the
drawing can be “hidden” while displaying
other features. This helps drawing produc-
tivity because objects can be temporarily
removed from the drawing without deleting
them to free up drawing space. In architec-
tural projects, different plans are commonly
placed on different layers within a single
drawing fi le. The fl oor plan, foundation plan,
and plumbing plan, for example, may each be
assigned to a separate layer. This provides a
way to plot different displays from a single
drawing.
Layers are typically named to reflect fl
their content. For example, all of the dimen-
sions in a drawing may be assigned to a layer
named Dims. In addition, each layer may
be assigned its own color. In many cases,
company or school standards specify layer
naming conventions and how to organize
drawing content.
Layers may also be assigned different
linetypes to distinguish content. A linetype is
a setting used to describe a line definition in fi
the Alphabet of Lines. Examples of linetypes
include the Object, Centerline, and Hidden
linetypes. When a line is drawn with a speci-
fied linetype, it has the same characteris- fi
tics as the equivalent line in the Alphabet of
Lines. Each linetype may have its own line-
weight setting to reflect the plotting thickness
desired. When using a plotter with pens, the
line thickness is determined by the size of the
plotter pen.
Drawing specifications such as layer and
linetype settings should be determined before
starting a project. Saved settings for layers,
linetypes, object snaps, and other CAD func-
tions can be specified in a drawing template
and used each time a new drawing is started.
Templates and setup commands are discussed
later in this chapter.
Blocks
One of the basic advantages of CAD is
never having to draw the same object twice.
For example, objects can be copied and
reused once they are drawn. Copying objects
is discussed later in this chapter. Another way
to avoid drawing objects repeatedly is to use
blocks. Blocks are predrawn objects designed
for multiple use in drawing projects. Once
something is drawn and saved as a block,
it can be inserted into a drawing as many
times as needed. This is a powerful function
that greatly increases drawing productivity.
Blocks are typically created for commonly
used symbols on drawings. For example,
blocks are commonly used on architectural
plan drawings to represent items such as
windows and doors.
Many companies store hundreds of
blocks in symbol libraries. A symbol library