In the following image:
To draw perpendicular from P on AB, the next step will be:
Join P to the mid-point of AB.
Join AP and BP and then join P to the mid-point of AB.
Draw arcs of equal length from A and B and let them intersect.
Join AP and BP.
Draw arcs of equal length from A and B and let them intersect.
Draw arcs of equal length from A and B and let them intersect.