Skew lines are lines that are not on the same plane, are not parallel and do not intersect. Some examples of skew line illustrations in geometry include two lines running through the opposite edges of a tetrahedron and a one-sheeted hyperboloid, which is obtained by revolving a line around three skew lines. In real life, skew lines can be observed in two street signs placed over each other and in a pedestrian overpass above a road or highway.
Considering the nature of skew lines, it is easier to visualize them in a three-dimensional way. Therefore, it is usually a challenge to illustrate skew lines on a computer screen or on paper. Drawing a diagram over a real-life image or a geometric figure is one of the best ways to show the presence of skew lines.
For example, drawing one upward arrow on the back side of a rectangular container and another arrow moving to the right on the front side of the container can effectively show how skew lines lie on different planes and are neither parallel nor intersecting. To further illustrate the concept of skew lines, imagine a person standing in a small closet, where he can touch two walls by stretching out his arms. If he had a marker on both hands and he draws a horizontal line on his left and a vertical line on his right, then both lines are skew lines.