line perpendicular to a plane

This is a picture of a door frame. It intersects with the floor (the plane) creating a 90^o  angle. The angle is perpendicular because a perpendicular angle is one that creates 90^o. This object was found in my house. You can find doorframes in almost any sheltered area. A doorframe is used as a passage from one room to another or can be a space for a door to fit.

-       I took this photo
     A door can be used in the industry of hospitality. In many restaurants the door shows the class of the restaurant.