Create and modify 3D models > Create 2D geometry > 2D guides or construction lines
  
2D guides or construction lines
Construction lines and circles help you draw profiles. They appear as magenta (dark pink) lines by default. Here you can see the magenta construction lines, a white profile, and a green workplane:
New users commonly try to apply Modeling commands (to create 3D geometry) such as Pull Linear or Pull Angular to construction lines; however, construction lines are ignored by commands that create 3D geometry.
To create construction lines, click Modeling and then, in the Draw group, use the Construction Line commands such as 2 Points or Parallel.
Help is available in the prompt line as you use each command.