Parallel and perpendicular lines

If you want to review the definition of PARALLEL and PERPENDICULAR lines, you can have a look here (or clic on the image)

 
Here you can find another good explanation: 

To practice how to draw parallel and perpendicular lines, have a look at the following video.

El siguiente vídeo puede ayudarte a practicar cómo dibujar líneas paralelas y perpendiculares utilizando la escuadra y el cartabón.