PRP PT allows you to create a line perpendicular to 
a selected entity, and through a specified point.

Select the desired entity, near the point of
perpendicularity.

Indicate the reference point that the perpendicular line
will pass through, using a Position Menu option.

An error message is displayed if you are constructing in 
3-D and the entities you select are not coplanar. You are
prompted to press <Enter> and to select the first entity.

If the reference point is on the selected entity and the 
L-LIMIT switch is set to FUNCTN, an error message is 
displayed indicating that the current settings and 
selections result in a zero-length line. If this message
is displayed, change the line limits, and press <Enter>,
or reselect the desired entity and reference point.

With the L-LIMIT switch set to FUNCTN, the perpendicular
line is created with the reference point and the
perpendicularity point as its endpoints.

If the reference point is on the selected entity and the 
L-LIMIT switch is set to VIEWPORT, the line is 
perpendicular to the selected entity at the specified
reference point, and the line extends to the screen 
limits.
