At the beginning of this lesson, you identified the types of lines that form a house's frame--the structure beneath the roof and walls. Let's take another look at the house, but this time we'll go inside after construction is complete. Like any other house, this one has walls and floors that are parallel to each other, perpendicular to each other, and skew with each other.

Use this slideshow to review how each line relationship appears in the world around you.

This room contains parallel lines - lines that do not intersect. Can you see them? In this reading room of the house, parallel lines can be seen in the walls behind the sofa. Can you see perpendicular lines? These lines will intersect at right angles and form a corner that looks like two sides of a square. In the living room of the house, an example of perpendicular lines can be seen where the mantel's corners meet with the fireplace. There are skew lines in this photo, can you find them? These lines do not cross, AND lie in different planes! In the empty dining room of the house, an example of skew lines can be seen in the two lines that lie in two different planes.