Choose Home tab→Solids group→Thin Wall list→Thin Region.
Click on the faces you want to thin.
On the command bar, type a value for the common wall thickness. This is the thickness you want to use for all or most of the part walls.
Click any faces you want to leave open, then click the Accept (check mark) button on the command bar.
Note:
You can use the Deselect (x) button on the command bar to clear selected faces.
Preview the feature by clicking the Preview button on the command bar.
Note:
If the feature is not what you wanted, you can return to any step to make adjustments. You can preview and alter the feature as many times as necessary before going to the Finish step.
Finish the feature.
Tip:
Open walls are optional. You can preview the feature any time after you define the common wall thickness.
You can select a capping face or faces for the thin feature. Click the Capping Faces button on the command bar to go to the Capping Faces step. Click the face(s) to use for the capping face and type a value in the Offset box if you want to define an offset from the capping face.
You can make some walls thicker or thinner than the common wall thickness. Click the Unique Thickness button on the command bar to go to the Unique Thickness step. Click the faces you want to apply the unique thickness to and type a unique thickness value in the command bar box.