Draw any line segment $\overline{ AB }.$ Mark any point $M$ on it. Through $M,$ draw a perpendicular to $\overline{ AB }.$

1. Draw a line segment $AB$ and mark a point $M$ on it.
2. With $M$ as centre and a convenient radius, construct an arc intersecting the line segment $AB$ at $P$ and $Q.$
3. With $P$ and $Q$ as centres and radius greater than $PM,$ construct $2$ arcs and mark the point of their intersection as $K.$ Join $MK.$
4. $\overline{ MK }$ is the required perpendicular through $M$ on $\overline{ AB }.$