The solution - the all mighty duct tape, a few thumb tacks, a bit of screen and a bit of ingenuity.
Here's how I did it:
• Measuring tape
• Straight edge (or metal ruler)
• Duct tape
• Thumb tacks
Step 1: Diagram
Above is a diagram my father-in-law made to better visualize this process. (Obrigado Moacyr!;-)