Perpendicular Lines
Perpendicular lines are lines that intersect to form right angles.
Example 1
This scene in the the movie Harry Potter and the Goblet of Fire takes place at the Hogwarts Owlery. Harry has just sent Hedwig off with a note to Sirius. The window frame is a set of perpendicular lines.
This scene is not in the books.
Example 2
This scene in the the movie Harry Potter and the Goblet of Fire takes place at the very beginning of the movie in Harry's dream about Voldemort, Bartemius "Barty" Crouch Junior, and Frank, the caretaker of The Riddle House. At this moment, Frank is walking up the stairs of the riddle house because he hears a noise in one of the upstairs rooms. The perpendicular lines are located on the wall.
"He let himself into the cavernous kitchen. Frank had not entered it for many years; nevertheless, although it was very dark, he remembered where the door into the hall was, and he groped his way toward it, his nostrils full of the smell of decay, ears pricked for any sound or footsteps or voices from overhead. He reached the hall, which was a little lighter owing to the large mullioned windows on either side of the front door, and started to climb the stairs, blessing the dust that lay thick upon the stone, because it muffled the sound of his feet and stick." -Harry Potter and the Goblet of Fire, Page 6