2012

Draw Construction Lines (and Rays)
Lines that extend to infinity in one or both directions, known as rays and
construction lines, respectively, can be used as references for creating other
objects.
For example, you can use construction lines to find the center of a triangle,
prepare multiple views of the same item, or create temporary intersections to
use for object snaps.
Infinite lines do not change the total area of the drawing. Therefore, their
infinite dimensions have no effect on zooming or viewpoints, and they are
ignored by commands that display the drawing extents. You can move, rotate,
and copy infinite lines just as you can move, rotate, and copy other objects.
You may want to create infinite lines on a construction line layer that can be
frozen or turned off before plotting.
Construction Lines
A construction line (also known as xlines) can be placed anywhere in
three-dimensional space. You can specify its orientation in several ways. The
default method for creating the line is the two-point method: you specify two
points to define the orientation. The first point, the root, is the conceptual
midpoint of the construction line, that is, the point snapped to by the
Midpoint object snap.
You can also create construction lines in several other ways.
 Horizontal and Vertical. Create construction lines that pass through
a point you specify and are parallel to the X or Y axis of the current UCS.
 Angle. Creates a construction line in one of two ways. Either you select
a reference line and then specify the angle of the construction line from
that line, or you create a construction line at a specific angle to the
horizontal axis by specifying an angle and then a point through which
the construction line should pass.
 Bisector. Creates a construction line that bisects an angle you specify.
You specify the vertex and the lines that create the angle.
 Offset. Creates a construction line parallel to a baseline you specify. You
specify the offset distance, select the baseline, and then indicate on which
side of the baseline to locate the construction line.
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