Line Perpendicular To A Plane

In this image of a line perpendicular to a plane, an old spice bottle was placed on the floor, old spice is used mainly as body wash. This object is perpendicular to the plane, in this case, the floor, because it is at a 90 degree angle to the plane. This object was found in my house. Many contractors need to use line perpendicular to a plane when building houses to make sure that the walls are straight.