This command is used to copy a portion of a polyline, at
specified points, and put the copied portion onto another layer.
The portion of existing polyline that is being copied still remains
as part of the original entity (with no break) , while the new
portion, with its chosen layer designation, is a new
polyline.
Pulldown Menu Location: Edit > Copy
Keyboard Command: copy_pl
Prerequisite: Polyline to be copied