Line Perpendicular to a Plane

This outline of an oil drill depicts a line perpendicular to a plane. In this case, the ground, or the blue line is the plane. The drill, or the green line, is the line perpendicular to a plane. Perpendicular means a line at an 90 degrees to a plane or another line.  I found this image on http://www.clker.com/clipart-oil-drill.html. Oil drills are used to mine oil internationally and are a vital part of the oil industry.