http://abduzeedo.com/fireworks-quick-tips-1-how-use-quickmask

One of the best functions we can use in Fireworks is Mask. It’s a basic command that can make our life easiser when working with images or when we need to hide some part of an object. In this tutorial we will create a Polaroid photo using amazing and inspirational illustrations from Adhemas. We already talked about him, but if you don’t know the work of this Brazilian artist yet, please check out his site after the tutorial!