Introduction to Flash MX Tutorial > Create and mask vector art > Create a mask |  |

Create a mask

The art that you created on the Shapes layer extends beyond the Stage, well into the canvas area. Although the area on the canvas won't appear in your published movie, the art beyond the Stage can be distracting in the authoring environment. While you can erase the part of the shapes that extend into the canvas, a better solution is to apply a mask over the Stage so that only the area under the mask—the entire Stage, in this case—remains visible. This way, if you'd like to return to the shapes to modify them, they will be intact.

1 | With the Shapes layer selected, add a new layer to the Timeline and name it Mask.
2 | In the toolbox, select the Rectangle tool and draw a rectangle that extends from the upper left corner of the Stage to the lower right corner.
| This rectangle is the shape of your mask. Anything under the rectangle will be visible.
3 | Right-click (Windows) or Control-click (Macintosh) the Mask layer name in the Timeline and choose Mask from the context menu.
| The layer is converted to a mask layer, indicated by a down arrow icon. The layer immediately below it is linked to the mask layer, and its contents show throughout the filled area on the mask. The masked layer name is indented, and its icon changes to a right-pointing arrow. The art on the canvas is no longer visible on the Stage.
| Mask layers must be locked for the Mask effect to show. To edit the shapes, you can unlock the Mask and Background Shapes layers. When you finish editing the art, lock the layers again to invoke masking.
4 | Save your file.