Hi to all, this is my first post. I have a projector and a pull down screen, i am trying to think of the best way to make removable masking that is also adjustable to suite the different aspect ratios. Has anyone got any ideas and what would be the best material for the masking. I thought of black velvet for the mask, but not sure about how to build a light frame work that can be adjusted and easily folded away when not in use. 
Any ideas would be gratefully received.
Thanks,
Chris.