Construction:
(i) Drawn a line segment PQ using scale and taken a point R outside of PQ.
(ii) Placed a set-square on PQ such that one arm of its right angle aligns along PQ.
(iii) Placed a scale along the other edge of the right angle of the set-square
(iv) Slide the set-square along the line till the point R touches the other arm of its right angle.
(v) Joined RS along the edge through R meeting PQ at S.
Hence RS ⊥ PQ.
