Draw any line segment. Take any point R not on it. Through R, draw a perpendicular to. (Use ruler and set-square)
(1) Take the given line segment and mark any point R outside.
(2) Place a set square on such that one arm of its right angle aligns along.
(3) Place the ruler along the edge opposite to the right angle of the set square.
(4) Hold the ruler fixed. Slide the set square along the ruler till the point R touches the other arm of the set square.
(5) Draw a line along this edge of the set square which will be passing through R. It is the required line, which is perpendicular to.