- 
       Click the Rib 
       icon
        . .
 The Rib dialog box that appears displays the Prism icon as the default shape to be created. Keep this option. icon as the default shape to be created. Keep this option.
 
- 
       Select Internal Ribs as the profile to be 
       used. 
- 
       Enter 20mm in the Length field to define the 
       first limit. 
- 
       In the Wall frame, set the Enter thickness 
		option.  Enter 1mm to define the wall thickness. Wall thickness values 
       can only by positive (nonzero) values. 
- 
       Click the Direction tab to ensure that the 
       direction of the features will be normal to the profile plane. 
- 
       Click the Draft tab. 
- 
       To define the draft angle, set the Draft behavior 
       option to Intrinsic to feature. Options are now displayed. 
- 
       Set the Angle option to -1deg. 
- 
       Set the Profile plane as the neutral element 
       to be used for drafting the rib feature. 
- 
       Click OK to create the rib. The specification tree indicates this operation under the 
       name of Rib.1. 
Ribs are typically applied inside of a shelled body.