Given a point not on the line it's possible to use a compass and straightedge to create a line perpendicular to that passes through That is, the unique line described by the Perpendicular Postulate.
First, place the sharp end of the compass at point and draw an arc that intersects at two distinct points. These points will be named and for later referencing.
Draw two arcs that intersect on the side of opposite to by placing the sharp end in and respectively, using the same distance on the compass for each arc.
Using a straightedge to draw a line through and the intersection of the arcs gives the desired perpendicular line.
The image can now be cleaned up to get the final result.