Masks are like windows or cut-outs: They reveal parts of images in layers below. For example, you can use text as a mask to reveal parts of an image within the shapes of the letters , as shown in Figure 16.4. Creating a mask is easy. Draw simple shapes on a layer above the layer you want to mask. When your mask shape is in place, (Ctrl+click) [right-click] the layer and then select Mask from the context menu. This applies the mask to the layer below and locks both the mask layer and the masked layer below it. To mask another layer with the same mask, drag and drop it under the mask layer. You can also (Ctrl+click) [right-click] the layer you want to mask, and select Properties, Masked.
Figure 16.4. Text can be used as a mask.
For more details on using masks, see "Working with Dynamic Masks," page 534 , in Chapter 20, "Basic ActionScript."
For more details on using masks, 