Chapter 12.1, Problem 9MC

To draw the perpendicular to a line $l$ through a point $P$ on the line, use a drafting triangle to align one of the legs of the triangle with the line, as shown in the figure. Next move the triangle along the leg until the other leg passes through the given point, $P$. The line $m$ is perpendicular to line $l$. Will the construction described above work if the point $P$ is not on line $l$ ? why or why not?