Tutorial to use rib feature in Autodesk Inventor?-Lesson 2
Sketch an L shape and exit the sketch mode.
Click on extrude command.
Extrude the profile to a certain limit according to your requirement.
Plane-> midplane between two parallel planes.
Select the two side planes to create a plane in the middle.
Invoke a new sketch on the plane.
sketch a line to perform the rib. Exit the sketch.
Click on rib.
Choose "parallel to sketch plane" option in the rib dilog box. Provide some thickness. Select the side to provide thickness or select axisymmetry.
Select "finite" to get a rib as shown in the figure.