Start with a line segment PQ and a point R off the line. 

1. Place the compasses on point R and set its width to a little more than the distance to the line PQ. The exact distance is not important. 

2. Draw a wide arc from the right of R around so it crosses the line PQ at two points.
Label the left point J 

3. Without adjusting the compasses' width, move the compasses to J and draw an arc across the line PQ. Label this point E. 

4. Without adjusting the compasses' width, move the compasses to E and draw an arc across the large arc to the right of R. Label this point S. 

5. Draw a straight line through points R and S. 

Done. The line RS is parallel to the line PQ 
