Part Modeling > Base Features > Extrude > Basics of the Extrude Feature > About the Cap with Model Geometry Option
  
About the Cap with Model Geometry Option
In some cases, there is more than one way to cap (close) a feature and attach it to the solid geometry. Use the Cap with model geometry option to specify how to cap and attach a thickened feature to the model, and to select which surface to use. This option is available under the following conditions:
Extrude or Revolve feature
Thicken is selected.
The sketch is an open sketch.
One or both sketch end points intersect the model solid geometry.
The system detects at least one surface that can be used to cap and attach the Extrude or Revolve feature to the model.
When the system detects at least one surface that can be used to attach the feature to the model, you can cap and attach the feature in one of two ways:
By default, the system tries to cap the thickened extrusion with model geometry. You can cycle through the available geometry by clicking Previous and Next.
 
* The sketch must intersect the solid geometry. The end point of the sketch must intersect either a reference you select, or the extension of the reference. When the end point of the sketch does not intersect the selected reference, but intersects the extension of the reference, you must add the desired capping geometry as references to the sketch.
If you do not want to cap the extrusion with existing model geometry, clear the Cap with model geometry check box. This caps the thickened extrusion with a surface that is normal to the end of the sketch.
Example: Extrude Feature
An open sketch intersects the solid geometry.
In this case, there are three options for capping and attaching the Extrude feature to the solid geometry:
Cap the thickened geometry with a surface that is normal to the end of the sketch, as if it is a free end that does not touch the model solid geometry
Cap the geometry using one of the surfaces that intersects with the sketch end point:
Top surface
Side surface
Example: Revolve Feature
An open sketch intersects the solid geometry.
In this case, there are three options for capping and attaching the Revolve feature to the solid geometry:
Cap the thickened geometry with a surface that is normal to the end of the sketch, as if it is a free end that does not touch the model solid geometry
Cap the geometry using one of the surfaces that intersects with the sketch end point:
Top surface
Side surface