Masking is used to clarify maps that are densely packed with annotation and symbology. You can use a polygon mask layer to hide particular aspects of one layer, and add a layer of map text and other symbols on top of it. The goal is to make the map more readable.
For example, in a geologic map, many polygons are symbolized with a fill pattern. Using a mask to remove the patterns around the text makes the map easier to read and use.
In an elevation map, contour lines and text may overlap each other. However, by using a mask for the annotation, sections of contour lines are hidden, while the elevation shading underneath those layers remains visible.
When you apply masking, one of your layers can be set to mask one or more other layers in your map. Any polygon feature class can be used as a masking layer.
- Select the layer you want to apply masking to in the Contents pane.
- On the Appearance tab, in the Drawing group, click Masking .
- In the drop-down menu, check all masking layers you want to apply as mask. If one of the layers already has a masking layer, the check box next to the masking layer will be in an intermediate state. Click the masking layer again to set it as the masking layer for all selected layers.