Draw a line l and a point X on it. Through X, draw a line segment XY perpendicular to l.

Now draw a perpendicular to at Y. (use ruler and compasses)

Steps of Construction-

1. Draw a line l and take point X on it.

2. With X as centre and a convenient radius, draw an arc intersecting the line l at two points A and B.

3. With A and B as centres and a radius greater than XA, draw two arcs, which cut each other at C.

4. Join XC and produce it to Y. Then XY is perpendicular to l.

5. With Y as centre and a convenient radius, draw an arc intersecting XY at two points C and D.

6. With C and D as centres and radius greater than YD, draw two arcs which cut each other at F.

7. Join YF, then YF is perpendicular to XY at Y.