Create panel > Shapes > Extended Splines > Object Type rollout > Angle
Create menu > Shapes > Angle
Use Angle to create a closed “L” shaped spline. You have the option to specify the radii of the corners between the vertical and horizontal legs of the section.
All spline-based shapes share these parameters. For explanations, see Splines and Extended Splines.
The Angle shape uses the standard creation methods of Center or Edge. Most spline-based shapes share the same Creation Method parameters. For explanations, see Splines and Extended Splines.

Length—Controls the height of the vertical leg of the angle.
Width—Controls the width of the horizontal leg of the angle.
Thickness—Controls the thickness of both legs of the angle.
Sync Corner Fillets—When turned on, Corner Radius 1 controls the radius of both the interior and exterior corners between the vertical and horizontal legs. It also maintains the thickness of the section. Default=on.
Corner Radius 1—Controls the exterior radius between the vertical and horizontal legs of the angle.
Corner Radius 2—Controls the interior radius between the vertical and horizontal legs of the angle.
Edge Radii—Controls the interior radius at the outermost edges of the vertical and horizontal legs.
Note: Take care when adjusting these settings. There are no constraining relationships between them. Therefore, it's possible to set an inside radius (Corner Radius 2) that is greater than the length or width of the legs of the angle.