Parallel Constraint

Makes the first selected line parallel to the second selected line.

1. Start with two lines. Activate the Parallel constraint and select the line you want to be made parallel.
   
2. Select the line to which you want the first line to be parallel.
   
   The lines are parallel, and the parallel constraint symbol is added to both lines.
   
3. If you edit either line, the parallel constraint will be maintained.