The Erase tool
            removes sculpting from a layer in the areas you stroke. Any sculpting
            on the original base mesh remains unaffected. 
         
         Note You can create a
               layer prior to any sculpting and use layers for all your sculpting
               until you need to merge or flatten them. In this way, the base mesh remains
               unaffected if you need to revert to it.
            
         
            - Select the Layers window
               and ensure the display button at the top is set to Sculpt.
            
- Click the layer whose sculpting you want
               to erase, ensuring that the layer is both visible and unlocked.
            
- Note the subdivision level on which the
               layer was first created as well as the currently displayed subdivision
               level, then press either the Page Up or Page
                  Down key to display the subdivision level that matches
               the layer subdivision level.
            
- Select the Sculpt Tools tray.
            
- Select the Erase tool,
               and stroke on the model in the areas you want to erase.